CHAPTER 3

MUTATIONS

Und was in schwankender Erscheinung schwebt,

Befestiget mit dauemden Gedanken.1 GOETHE

'JUMP-LIKE' MUTATIONS-THE WORKING-GROUND

OF NATURAL SELECTION

The general facts which we have just put forward in evidence

of the durability claimed for the gene structure, are perhaps

too familiar to us to be striking or to be regarded as convincing.

Here, for once, the common saying that exceptions prove the

rule is actually true. If there were no exceptions to the likeness

between children and parents, we should have been deprived

not only of all those beautiful experiments which have revealed

to us the detailed mechanism of heredity, but also of that grand,

million-fold experiment of Nature, which forges the species

by natural selection and survival of the fittest.

Let me take this last important subject as the starting-point

for presenting the relevant facts-again with an apology and a

reminder that I am not a biologist:

We know definitely, today, that Darwin was mistaken in

regarding the small, continuous, accidental variations, that are

bound to occur even in the most homogeneous population, as

the material on which naturaLselection works. For it has been

proved that they are not inherited. The fact is important

enough to be illustrated briefly. If you take a crop of purestrain

barley, and measure, ear by ear, the length of its awns and

plot the result of your statistics, you will get a bell-shaped

curve as shown in Fig. 7, where the number of ears with a

1 And what in fluctuating appearance hovers,

Ye shall fix by lasting thoughts.

Mutations 35

definite length of awn is plotted against that length. In other

words: a definite medium length prevails, and deviations in

either direction occur with certain frequencies. Now pick out

a group of ears (as indicated by blackening) with awns noticeably

beyond the average, but sufficient in number to be sown

in a field by themselves and give a new crop. In making the

same statistics for this, Darwin would have expected to find

f .u... .

0 ...,. .

'a z

t

'~ ....

-

-

_f

- Length of awns

..._.

-

-

-,_ -- -·

Fig. 7. Statistics of length of awns in a pure-bred crop. The black group is to be

selected for sowing. (The details are not from an actual experiment, but are just

set up for illustration.)

the corresponding curve shifted to the right. In other words, he

would have expected to produce by selection an increase of the

average length of the awns. That is not the case, if a truly purebred

strain of barley has been used. The new statistical curve,

obtained from the selected crop, is identical with the first one,

and the same would be the case if ears with particularly short

awns had been selected for seed. Selection has no effectbecause

the small, continuous variations are not inherited.

They are obviously n9t based on the structure of the hereditary

substance, they are accidental. But about forty years ago the

What is Life?

Dutchman de Vries discovered that in the offspring even of

thoroughly pure-bred stocks, a very small number of individuals,

say two or three in tens of thousands, turn up with small but

'jump-like' changes, the expression 'jump-like' not meaning

that the change is so very considerable, but that there is a discontinuity

inasmuch as there are no intermediate forms between

the unchanged and the few changed. De Vries called that

a mutation. The significant fact is the discontinuity. It reminds

a physicist of quantum theory-no intermediate energies

occurring between two neighbouring energy levels. He would

be inclined to call de Vries's mutation theory, figuratively, the

quantum theory of biology. We shall see later that this is much

more than figurative. The mutations are actually due to quantum

jumps in the gene molecule. But quantum theory was but

two years old when de Vries first published his discovery, in

1902. Small wonder that it took another generation to discover

the intimate connection I

THEY BREED TRUE, THAT IS,

THEY ARE PERFECTLY INHERITED

Mutations are inherited as perfectly as the original, unchanged

characters were. To give an example, in the first crop of barley

considered above a few ears might tum up with awns considerably

outside the range of variability shown in Fig. 7, say

with no awns at all. They might represent a de Vries mutation

and would then breed perfectly true, that is to say, all their

descendants would be equally awnless.

Hence a mutation is de.finitely a change in the hereditary

treasure and has to be accounted for by some change in the

hereditary substance. Actually most of the important breeding

experiments, which have revealed to us the mechanism of

heredity, consisted in a careful analysis of the offspring obMutations

37

tained by crossing, acc@rding to a preconceived plan, mutated

( or, in many cases, multiply mutated) with non-mutated or with

differently mutated individuals. On the other hand, by virtue

of their breeding true, mutations are a suitable material on

which natural sdection may work and produce the species as

described by Darwin, by eliminating the unfit and letting the

fittest survive. In Darwin's theory, you just have to substitute

'mutations' for his 'slight accidental variations' Gust as quantum

theory substitutes 'quantum jump' for 'continuous transfer

of energy'). ][n all other respects little change was necessary

in Darwin's theory, that is, if I am correctly interpreting the

view held by the majority of biologists.1

LOCALIZATION. RECESSIVITY AND DOMINANCE

We must now review some other fundamental facts and notions

about mutations, again in a slightly dogmatic manner, without

showing directly how they spring, one by one, from experimental

evidence.

We should expect a definite observed mutation to be caused

by a change in a definite r~gion in one of the chromosomes.

And so it is. It is important to state that we know definitely that

it is a change in one chromosome only, but not in the corresponding

'locus'· of the homologous chromosome. Fig. 8 indicates

this schematically, the cross denoting the mutated locus.

The fact that only one chromosome is affected is revealed when

the mutated individual ( often called 'mutant') is crossed with a

non-mutated one. For exactly half of the offspring exhibit the

1 Ample discussion has been given to the question, whether natural selection be

aided (if not superseded) by a marked inclination of mutations to take place in

a useful or favourable direction. My personal view about this is of no moment;

but it is necessary to state that the eventuality of' directed mutations' has been

disregarded in all the following. Moreover, I cannot enter here on the interplay

of 'switch' genes .and 'polygenes', however important it be for the actual

mechanismo f sele,:tiona nde volution.

What is Life?

mutant character and half the normal one.

That is what is to be expected as a consequence

of the separation of the two chromosomes on

meiosis in the mutant-as shown, very

schematically, in Fig. 9. This is a 'pedigree',

representing every individual ( of three consecutive

generations) simply by the pair of

chromosomes in question. Please realize that

if the mutant had both its chromosomes

affected, all the children would receive the

same (mixed) inheritance, different from that

of either parent. Fig. 8. Heterozygous

mutant. The cross

marks the mutated

But experimenting in this domain is not as

simple as would appear from what has just

gene.

been said. It is complicated by the second

important fact, viz. that mutations are very often latent. What

does that mean?

In the mutant the two 'copies of the code-script' are no

Fig. 9. Inheritance of a mutation. The straight lines across indicate the transfer

of a chromosome, the double ones that of the mutated chromosome. The un•

accounted-for chromosomes of the third generation come from the mates of the

second generation, which are iwt included in the diagram. They are supposed to

be non-relatives, free of the mutation.

Mutations 39

longer identical; they present two different 'readings' or

'versions', at any rate in that one place. Perhaps it is well to

point out at once that, while it might be tempting, it would

nevertheless be entirely wrong to regard the original version as

'orthodox', and the mutant version as 'heretic'. We have to

regard them, in principle, as being of equal

right-for the normal characters have also

arisen from mutations.

What actually happens is that the 'pattern'

of the individual, as a general rule, follows

either the one or the other version, which

may be the normal or the mutant one. The

version which is followed is called dominant,

the other recessive; in other words, the

mutation is called dominant or recessive,

according to whether it is immediately effective

in changing the pattern or not.

Recessive mutations are even more

frequent than dominant ones and are very

important, though at first they do not show

up at all. To affect the pattern, they have to

be present in both chromosomes(seeFig. 10).

Such individuals can be produced when two

equal recessive mutants happen to be crossed

with each other or when a mutant is crossed

Fig. 10. Homozygous

mutant, obtained

in one-quarter of

the descendants

either from selffertilization

of a

heterozygous :-'.:.Utant

(see Fig. 8) or

from crossing two

of them.

with itself; this is possible in hermaphroditic plants and even

happens spontaneously. An easy reflection shows that in these

cases about one-quarter of the offspring will be of this type and

thus visibly exhibit the mutated pattern.

What is Life .2

INTRODUCING SOME TECHNICAL LANGUAGE

I think it will make for clarity to explain here a few technical

terms. For what I called 'version of the code-script '-be it the

original one or a mutant one-the term' allele' has been adopted.

When the versions are different, as indicated in Fig. 8, the individual

is called heterozygous, with respect to that locus. When

they are equal, as in the non-mutated individual or in the case of

Fig. IO, they are called homozygous. Thus a recessive allele

influences the pattern only when homozygous, whereas a

dominant allele produces the same pattern, whether homozygous

or only heterozygous.

Colour is very often dominant over lack of colour (or white).

Thus, for example, a pea will flower white only when it has the

'recessive allele responsible for white' in both chromosomes in

question, when it is 'homozygous for white'; it will then breed

true, and all its descendants will be white. But one 'red allele'

( the other being white; 'heterozygous') will make it flower red,

and so will two red alleles ('homozygous'). The difference of

the latter two cases will only show up in the offspring, when the

heterozygous red will produce some white descendants, and the

homozygous red will breed true.

The fact that two individuals may be exactly alike in their

outward appearance, yet differ in their inheritance, is so important

that an exact differentiation is desirable. The geneticist

says they have the same phenotype, but different genotype. The

contents of the preceding paragraphs could thus be summarized

in the brief, but highly technical, statement:

A recessive allele influences the phenotype only when the

genotype is homozygous.

We shall use these technical expressions occasionally, but

shall recall their meaning to the reader where necessary.

Mutations 41

THE HARMFUL EFFECT OF CLOSE-BREEDING

Recessive mutations, as long as they are only heterozygous, are

of course no working-ground for natural selection. If they are

detrimental, as mutations very often are, they will nevertheless

not be eliminated, because they are latent. Hence quite a host

of unfavourable mutations may accumulate and do no immediate

damage. But they are, of course, transmitted to half of

the offspring, and that has an important application to man,

cattle, poultry or any other species, the good physical qualities

of which are of immediate concern to us. In Fig. 9 it is assumed

that a male individual (say, for concreteness, myself) carries

such a recessive detrimental mutation heterozygously, so that

it does not show up. Assume that my wife is free ofit. Then half

of our children (second line) will also carry it-again heterozygously.

If all of them are again mated with non-mutated partners

( omitted from the diagram, to avoid confusion), a quarter of

our grandchildren, on the average, will be affected in the same

way.

No danger of the evil ever becoming manifest arises, unless

equally affected individuals a:re crossed with each other, when,

as an easy reflection shows, one-quarter of their children, being

homozygous, would manifest the damage. Next to selffertilization

(only possible in hermaphrodite plants) the greatest

danger would be a marriage between a son and a daughter of

mine. Each of them standing an even chance of being latent! y

affected or not, one-quarter of these incestuous unions would

be dangerous inasmuch as one-quarter of its children would

manifest the damage. The danger factor for an incestuously bred

child is thus r : r 6.

In the same way the danger factor works out to be r : 64 for

the offspring of a union between two ('clean-bred') grandchildren

of mine who are first cousins. These do not seem to be

42 What is Life?

overwhelming odds, and actually the second case is usually

tolerated. But do not forget that we have analysed the consequences

of only one possible latent injury in one partner of the

ancestral couple (' me and my wife'). Actually both of them are

quite likely to harbour more than one latent deficiency of this

kind. If you know that you yourself harbour a definite one, you

have to reckon with 1 out of 8 of your first cousins sharing it!

Experiments with plants and animals seem to indicate that in

addition to comparatively rare deficiencies of a serious kind,

there seem to be a host of minor ones whose chances combine

to deteriorate the offspring of close-breeding as a whole. Since

we are no longer inclined to eliminate failures in the harsh way

the Lacedemonians used to adopt in the Taygetos mountain,

we have to take a particularly serious view about these things

in the case of man, where natural selection of the fittest is largely

retrenched, nay, turned to the contrary. The anti-selective effect

of the modern mass slaughter of the healthy youth of all

nations is hardly outweighed by the consideration that in more

primitive conditions war may have had a positive value in

letting the fittest tribe survive.

GENERAL AND HISTORICAL REMARKS

The fact that the recessive allele, when heterozygous, is completely

overpowered by the dominant and produces no visible

effect at all, is amazing. It ought at least to be mentioned that

there are exceptions to this behaviour. When homozygous

white snapdragon is crossed with, equally homozygous, crimson

snapdragon, all the immediate descendants are intermediate in

colour, i.e. they are pink (not crimson, as might be expected). A

much more important case of two alleles exhibiting their influence

simultaneously occurs in blood-groups-but we cannot

enter into that here. I should not be astonished if at long last

Mutations 43

recessivity should turn out to be capable of degrees and to

depend on the sensitivity of the tests we apply to examine the

'phenotype'.

This is perhaps the place for a word on the early history of

genetics. The backbone of the theory, the law of inheritance,

to successive generations, of properties in which the parents

differ, and more especially the important distinction recessivedominant,

are due to the now world-famous Augustinian

Abbot Gregor Mendel (1822-84). Mendel knew nothing about

mutations and chromosomes. In his cloister gardens in Brunn

(Brno) he made experiments on the garden pea, of which he

reared different varieties, crossing them and watching their

offspring in the 1st, 2nd, 3rd, ... , generation. You might say, he

experimented with mutants which he found ready-made in

nature. The results he published as early as 1866 in the Proceedings

of the N aturforschendeVr ereini n Brunn. Nobody seems

to have been particularly interested in the abbot's hobby, and

nobody, certainly, had the faintest idea that his discovery would

in the twentieth century become the lodestar of an entirely new

branch of science, easily the most interesting of our days. His

paper was forgotten and was only rediscovered in 1900, simultaneously

and independently, by Correns (Berlin), de Vries

(Amsterdam) and Tschermak (Vienna).

THE NECESSITY OF MUTATION BEING

A RARE EVENT

So far we have tended to fix our attention on harmful mutations,

which may be the more numerous; but it must be definitely

stated that we do encounter advantageous mutations as well. If a

spontaneous mutation is a small step in the development of the

species, we get the impression that some change is 'tried out'

in rather a haphazard fashion at the risk of its being injurious,

44 What is Life?

in which case it is automatically eliminated. This brings out

one very important point. In order to be suitable material for the

work of natural selection, mutations must be rare events, as

they actually are. If they were so frequent that there was a

considerable chance of, say, a dozen of different mutations

occurring in the same individual, the injurious ones would, as a

rule, predominate over the advantageous ones and the species,

instead of being improved by selection, would remain unimproved,

or would perish. The comparative conservatism

whici1 results from the high degree of permanence of the genes is

essential. An analogy might be sought in the working of a large

manufacturing plant in a factory. For developing better

methods, innovations, even if as yet unproved, must be tried

out. But in order to ascertain whether the innovations improve

or decrease the output, it is essential that they should be introduced

one at a time, while all the other parts of the mechanism

are kept constant.

MUTATIONS INDUCED BY X-RAYS

\Ve now have to review a most ingenious series of genetical

research work, which will prove to be the most relevant feature

of our analysis.

The percentage of mutations in the offspring, the so-called

mutation rate, can be increased to a high multiple of the small

natural mutation rate by irradiating the parents with X-rays or

y-rays. The mutations produced in this way differ in no way

(except by being more numerous) from those occurring spontaneously,

and one has the impression that every 'natural'

mutation can also be induced by X-rays. In Drosophila many

special mutations recur spontaneously again and again in the

vast cultures; they have been located in the chromosome, as

described on pp. 28-30, and have been given special names.

Mutations 45

There have been found even what are called 'multiple alleles',

that is to say, two or more different 'versions' and 'readings'in

addition to the normal, non-mutated one-of the same place

in the chromosome code; that means not only two, but three or

more alternatives in that particular' locus', any two of which are

to each other in the relation 'dominant-recessive' when they

occur simultaneously in their corresponding loci of the two

homologous chromosomes.

The experiments on X-ray-produced mutations give the

impression that every particular 'transition', say from the

normal individual to a particular mutant, or conversely, has its

individual 'X-ray coefficient'~ indicating the percentage of the

offspring which turns out to have mutated in that particular

way, when a unit dosage of X-ray has been applied to the

parents, before the offspring was engendered.

FIRS'T LAW. MUT ATI'ON IS A SINGLE EVENT

Furthermore, the laws governing the induced mutation rate

are extremely simple and extremely illuminating. I follow here

the report of N. W. Timofeeff, in Biological Reviews, vol. IX,

1934. To a considerable extent it refers to that author's own

beautiful work. The first law :is

( 1) The increase is exact!)' proportional to the dosage of

rays, so that one can actually speak [ as I did] of a coefficient of

tncrease.

We are so used to simple proportionality that we are liable

to underrate the far-reaching ,consequences of this simple law.

To grasp them, we may remember that the price of a commodity,

for example, is not always proportional to its amount.

In ordinary times a shopkeeper may be so much impressed by

your having: bought six oranges from him, that, on your deciding

to take after all a whole dozen, he may give it to you

What is Life .2

for less than double the price of the six. In times of scarcity

the opposite may happen. In the present case, we conclude that

the first half-dosage of radiation, while causing, say, one out of a

thousand descendants to mutate, has not influenced the rest at

all, either in the way of predisposing them for, or ofimmunizing

them against, mutation. For otherwise the second half-dosage

would not cause again just one out of a thousand to mutate.

Mutation is thus not an accumulated effect, brought about by

consecutive small portions of radiation reinforcing each other.

It must consist in some single event occurring in one chromosome

during irradiation. What kind of event?

SECOND LAW. LOCALIZATION OF THE EVENT

This is answered by the second law, viz.

(2) If you vary the quality of the rays (wave-length) within

wide limits,ftom soft X-rays to fairly hardy-rays, the coefficient

remains constant, provided you give the same dosage in so-called

r-units, that is to say, provided you measure the dosage by

the total amount of ions produced per unit volume in a suitably

chosen standard substance during the time and at the place

where the parents are exposed to the rays.

As standard substance one chooses air not only for convenience,

but also for the reason that organic tissues are composed

of elements of the same atomic weight as air. A lower

limit for the amount of ionizations or allied processes1 ( excitations)

in the tissue is obtained simply by multiplying the number

of ionizations in air by the ratio of the densities. It is thus

fairly obvious, and is confirmed by a more critical investigation,

that the single event, causing a mutation, is just an ionization

( or similar process) occurring within some 'critical' volume of

1 A lower limit, because these other processes escape the ionization measurement,

but may be efficient in producing mutations.

Mutations 47

the germ cell. What is the size of this critical volume? It can

be estimated from the observed mutation rate by a consideration

of this kind: if a dosage of 50,000 ions per ems produces a

chance of only I: 1000 for any particular gamete (that finds

itself in the irradiated district) to mutate in that particular way,

we conclude that the critical volume, the' target' which has to be

'hit' by an ionization for that mutation to occur, is only 1 lo O of

50 boo of a ems, that is to say, one fifty-millionth of a ems. The

numbers are not the right ones, but are used only by way of

illustration. In the actual estimate we follow M. Delbri.ick, in a

paper by Delbri.ick, N. W. Timofeeff and K. G. Zimmer,1

which will also be the principal source of the theory to be expounded

in the following two chapters. He arrives there at a

size of only about ten average atomic distances cubed, containing

thus only about 108 = a thousand atoms. The simplest

interpretation of this result is that there is a fair chance of producing

that mutation when an ionization ( or excitation) occurs

not more than about' 10 atoms away' from some particular spot

in the chromosome. We shall discuss this in more detail

presently.

The Timofeeff report contains a practical hint which I cannot

refrain from mentioning here, though it has, of course, no

bearing on our present investigation. There are plenty of

occasions in modern life when a human being has to be exposed

to X-rays. The direct dangers involved, as burns, X-ray cancer,

sterilization, are well known, and protection by lead screens,

lead-loaded aprons, etc., is provided, especially for nurses and

doctors who have to handle the rays regularly. The point is,

that even when these imminent dangers to the individual are

successfully warded off, there appears to be the indirect rlanger

of small detrimental mutations being produced in the germ cells

-mutations of the kind envisaged when we spoke of the un-

1 Nachr. a. d. Biologic d. Ges. d. Wiss. Gottingen, I (1935), 189.

What is Life?

favourable results of close-breeding. To put it drastically,

though perhaps a little nai:vely, the injuriousness of a marriage

between first cousins might very well be increased by the fact

that their grandmother had served for a long period as an X-ray

nurse. It is not a point that need worry any individual personally.

But any possibility of gradually infecting the human race

with unwanted latent mutations ought to be a matter of concern

to the community.

CHAPTER 4

THE Q~UANTUM-MECHANICAL

EVIDENCE

Und deines Geistes hochster Feuerflug

Hat schon am Gleichnis, hat am Bild genug.1 GOETHE

PERMANENCE L'NEXPLAINABLE BY CLASSICAL PHYSICS

Thus, aided by the marvellously subtle instrument of X-rays

(which, as the physicist remembers, revealed thirty years ago

the detailed atomic lattice structures of crystals), the united

efforts of biologists and physicists have of late succeeded in

reducing the upper limit for the size of the microscopic structure,

being responsible for a definite large-scale feature of the

individual--the ':size of a gene '-and reducing it far below the

estimates obtained on pp. 3c>-I. We are now seriously faced

with the question: How can we, from the point of view of

statistical physics:, reconcile the facts that the gene structure

seems to involve only a comparatively small number of atoms

(of the order of 1,000 and possibly much less), and that nevertheless

it displays a most regular and lawful activity-with a

durability or permanence that borders upon the miraculous?

Let me throw the truly amazing situation into relief once

again. Several members of the Habsburg dynasty have a peculiar

disfigurement of the lower lip (' Habsburger Lippe'). Its

inheritance has been studied carefully and published, complete

with historical portraits, by the Imperial Academy of Vienna,

under the auspices of the family. The feature proves to be a

genuinely j\1endelian 'allele' to the normal form of the lip.

Fixing our attention on the portraits of a member of the family

1 And thy spirit's fiery flight of imagination acquiesces in an image, in a parable.

50 What is Life .2

in the sixteenth century and of his descendant, living in the

nineteenth, we may safely assume that the material gene

structure, responsible for the abnormal feature, has been carried

on from generation to generation through the centuries, faithfully

reproduced at every one of the not very numerous cell

divisions that lie between. Moreover, the number of atoms involved

in the responsible gene structure is likely to be of the

same order of magnitude as in the cases tested by X-rays. The

gene has been kept at a temperature around 98 °F during all that

time. How are we to understand that it has remained unperturbed

by the disordering tendency of the heat motion for

centuries?

A physicist at the end of the last century would have been at a

loss to answer this question, if he was prepared to draw only

on those laws of Nature which he could explain and which he

really understood. Perhaps, indeed, after a short reflection on

the statistical situation he would have answered ( correctly, as

we shall see): These material structures can only be molecules.

Of the existence, and sometimes very high stability, of these

associations of atoms, chemistry had already acquired a widespread

knowledge at the time. But the knowledge was purely

empirical. The nature of a molecule was not understood-the

strong mutual bond of the atoms which keeps a molecule in

shape was a complete conundrum to everybody. Actually, the

answer proves to be correct. But it is of limited value as long as

the enigmatic biological stability is traced back only to an

equally enigmatic chemical stability. The evidence that two

features, similar in appearance, are based on the same principle,

is always precarious as long as the principle itself is unknown.

Quantum-MechanicaEl vidence 51

EXPLICABLE BY QUANTUM THEORY

In this case it is supplied by quantum theory. In the light of

present knowledge, the mechanism of heredity is closely

related to, nay, founded on, the very basis of quantum theory.

This theory was discovered by Max Planck in 1900. Modern

genetics can be dated from the rediscovery of Mendel's paper

by de Vries, Correns and Tschermak (1900) and from de Vries's

paper on mutations (1901-3). Thus the births of the two great

theories nearly coincide, and it is small wonder that both of

them had to reach a certain maturity before the connection

could emerge. On the side of quantum theory it took more

than a quarter of a century till in 1926-7 the quantum theory

of the chemical bond was outlined in its general principles by

W. Heider and F. London. The Heider-London theory involves

the most subtle and intricate conceptions of the latest

development of quantum theory ( called 'quantum mechanics'

or 'wave mechanics'). A presentation without the use of calculus

is well-nigh impossible or would at least require another

little volume like this. But fortunately, now that all work has

been done and has served to clarify our thinking, it seems to be

possible to point out in a more direct manner the connection

between 'quantum jumps' and mutations, to pick out at the

moment the most conspicuous item. That is what we attempt

here.

QUANTUM THEORY-DISCRETE STATESQUANTUM

JUMPS

The great revelation of quantum theory was that features of

discreteness were discovered in the Book of Nature, in a context

in which anything other than continuity seemed to be

absurd according to the views held until then.

The first case of this kind concerned energy. A body on the

What is Life .2

large scale changes its energy continuously. A pendulum, for

instance, that is set swinging is gradually slowed down by the

resistance of the air. Strangely enough, it proves necessary to

admit that a system of the order of the atomic scale behaves

differently. On grounds upon which we cannot enter here, we

have to assume that a small system can by its very nature possess

only rPrtain discrete amounts of energy, called its peculiar

energy levels. The transition from one state to another is a

rather mysterious event, which is usually called a 'quantum

jump'.

But energy is not the only characteristic of a system. Take

again our pendulum, but think of one that can perform different

kinds of movement, a heavy ball suspended by a string from the

ceiling. It can be made to swing in a north-south or east-west

or any other direction or in a circle or in an ellipse. By gently

blowing the ball with a bellows, it can be made to pass continuously

from one state of motion to any other.

For small-scale systems most of these or similar characteristics-

we cannot enter into details-change discontinuously.

They are 'quantized', just as the energy is.

The result is that a number of atomic nuclei, including their

bodyguards of electrons, when they find themselves close to

each other, forming 'a system', are unable by their very nature

to adopt any arbitrary configuration we might think of. Their

very nature leaves them only a very numerous but discrete

series of' states' to choose from.1 We usually call them levels or

energy levels, because the energy is a very relevant part of the

characteristic. But it must be understood that the complete

description includes much more than just the energy. It is

1 I am adopting the version which is usually given in popular treatment and

which suffices for our present purpose. But I have the bad conscience of one

who perpetuates a convenient error. The true story is much more complicated,

inasmuch as it includes the occasional indeterminateness with regard to the

state the system is in.

!,~uantum-MechanicEavli dence 53

virtually correct to think of a state as meaning a definite configuration

of all the corpuscles.

The transition from one of these configurations to another

is a quantum jump. If the second one has the greater energy

(' is a higher level'), the system must be supplied from outside

with at least the difference of the two energies to make the

transition possible. To a lower level it can change spontaneously,

spending the surplus of energy in radiation.

MOLECULES

Among the discrete set of states of a given selection of atoms

there need not necessarily 'but there may be a lowest level,

implying a clos1:a::p proach of the nuclei to each other. Atoms

in such a state form a molecule. The point to stress here is, that

the molecule will of necessity have a certain stability; the configuration

cannot change, unless at least the energy difference,

necessary to 'lift' it to the next higher level, is supplied from

outside. Hence this level difference, which is a well-defined

quantity, determines quantitatively the degree of stability of

the molecule. It will be observed how intimately this fact is

linked with the very basis of quantum theory, viz. with the

discreteness of the level scheme.

I must beg the reader to take it for granted that this order of

ideas has been thoroughly checked by chemical facts; and that

it has proved successful in explaining the basic fact of chemical

valency and many details about the structure of molecules, their

binding-energies, their stabilities at different temperatures, and

so on. I am speaking of the Heider-London theory, which, as I

said, cannot be e:xamined in detail here.

54 What is Life .2

THEIR STABILITY DEPENDENT ON TEMPERATURE

We must content ourselves with examining the point which is of

paramount interest for our biological question, namely, the

stability of a molecule at different temperatures. Take our

system of atoms at first to be actually in its state oflowest energy.

The physicist would call it a molecule at the absolute zero of

temperature. To lift it to the next higher state or level a definite

supply of energy is required. The simplest way of trying to

supply it is to 'heat up' your molecule. You bring it into an

environment of higher temperature(' heat bath'), thus allowing

other systems (atoms, molecules) to impinge upon it. Considering

the entire irregularity of heat motion, there is no sharp

temperature limit at which the 'lift' will be brought about with

certainty and immediately. Rather, at any temperature (different

from absolute zero) there is a certain smaller or greater

chance for the lift to occur, the chance increasing of course

with the temperature of the heat bath. The best way to express

this chance is to indicate the average time you will have to wait

until the lift takes place, the 'time of expectation'.

From an investigation, due to M. Polanyi and E. Wigner,1

the 'time of expectation' largely depends on the ratio of two

energies, one being just the energy difference itself that is

required to effect the lift (let us write W for it), the other one

characterizing the intensity of the heat motion at the temperature

in question (let us write T for the absolute temperature

and kT for the characteristic energy).2 It stands to reason that

the chance for effecting the lift is smaller, and hence that the

time of expectation is longer, the higher the lift itself compared

with the average heat energy, that is to say, the greater the

ratio W:kT. What is amazing is how enormously the time of

1 Zeitschrift fiir Physik, Chemie (A), Haber-Band (1928), p. 439.

11 k is a numerically known constant, called Boltzmann's constant; ikT is the

average kinetic energy of a gas atom at temperature T.

Quantum-MechanicaEl vidence 55

expectation depends on comparatively small changes of the

ratio W: kT. To give an example (following Delbriick): for W

thirty times kT the time of expectation might be as short as

lo s., but would rise to 16 months when Wis 50 times kT, and

to 30,000 years when Wis 60 times kT 1

MATHEMATICAL INTERLUDE

It might be as well to point out in mathematical language-for

those readers to whom it appeals-the reason for this enormous

sensitivity to changes in the level step or temperature, and to add

a few physical remarks of a similar kind. The reason is that the

time of expectation, call it t, depends on the ratio W/kT by an

exponential function, thus

t = -reW/kT.

-r is a certain small constant of the order of 10- 13 or rn- 14 s.

Now, this particular exponential function is not an accidental

feature. It recurs again and again in the statistical theory of

heat, forming, as it were, its backbone. It is a measure of the

improbability of an energy amount as large as W gathering

accidentally in some particular part of the system, and it is this

improbability which increases so enormously when a considerable

multiple of the 'average energy' kT is required.

Actually a W = 3okT (see the example quoted above) is

already extremely rare. That it does not yet lead to an enormously

long time of expectation ( only -h s. in our example) is,

of course, due to the smallness of the factor -r. This factor has a

physical meaning. It is of the order of the period of the vibrations

which take place in the system all the time. You could, very

broadly, describe this factor as meaning that the chance of

accumulating the required amount W, though very small,

recurs again and again' at every vibration', that is to say, about

10 13 or 10 14 times during every second.

56 What is Life .2

FIRST AMENDMENT

In offering these considerations as a theory of the stability of

the molecule it has been tacitly assumed that the quantum

jump which we called the 'lift' leads, if not to a complete

disintegration, at least to an essentially different configuration

of the same atoms-an isomeric molecule, as the chemist

would say, that is, a molecule composed of the same atoms in a

different arrangement (in the application to biology it is going

to represent a different 'allele' in the same 'locus' and the

quantum jump will represent a mutation).

To allow of this interpretation two points must be amended

in our story, which I purposely simplified to make it at all

intelligible. From the way I told it, it might be imagined that

only in its very lowest state does our group of atoms form

what we call a molecule and that already the next higher state

is 'something else'. That is not so. Actually the lowest level is

followed by a crowded series of levels which do not involve

any appreciable change in the configuration as a whole, but

only correspond to those small vibrations among the atoms

which we have mentioned on p. 55. They, too, are 'quantized',

but with comparatively small steps from one level to the next.

Hence the impacts of the particles of the 'heat bath' may suffice

to set them up already at fairly low temperature. If the molecule

is an extended structure, you may conceive these vibrations as

high-frequency sound waves, crossing the molecule without

doing it any harm.

So the first amendment is not very serious : we have to disregard

the 'vibrational fine-structure' of the level scheme. The

term 'next higher level' has to be understood as meaning the

next level that corresponds to a relevant change of configuration.

Q]eantum-MechanicEavl idence 57

SECOND AMENDMENT

The second amendment is far more difficult to explain, because

it is concerned with certain vital, but rather complicated,

features of 1the scheme of relevantly different levels. The free

passage between two of them may be obstructed, quite apart

from the required energy supply; in fact, it may be obstructed

even from the hif~her to the lower state.

H--I_I_I_O--H

l l l

Fig. 1 L The two isomeres of propyl-alcohol.

Let us start from the empirical facts. It is known to the

chemist that the same group of atoms can unite in more than

one way to form a molecule. Such molecules are called isomeric

(' consisting of the same parts'; io-os = same, μepos = part).

Isomerism :is not an exception, it is the rule. The larger the

molecule, the more isomeric alternatives are offered. Fig. I I

shows one of the simplest cases, the two kinds of propylalcohol,

both consisting of 3 carbons (C), 8 hydrogens (H),

3 iWl

58 What is Life .2

I oxygen (0). 1 The latter can be interposed between any hydrogen

and its carbon, but only the two cases shown in our figure

are different substances. And they really are. All their physical

and chemical constants are distinctly different. Also their

energies are different, they represent ' different levels'.

3

1

Fig. 12. Energy threshold (3) between the isomeric levels (1) and (2). The arrows

indicate the minimum energies required for transition.

The remarkable fact is that both molecules are perfectly

stable, both behave as though they were 'lowest states'. There

are no spontaneous transitions from either state towards the

other.

The reason is that the two configurations are not neighbouring

configurations. The transition from one to the other can

only take place over intermediate configurations which have a

greater energy than either of them. To put it crudely, the oxygen

has to be extracted from one position and has to be inserted into

the other. There does not seem to be a way of doing that without

passing through configurations of considerably higher

1 Models, in which C, Hand O were represented by black, white and red wooden

balls respectively, were exhibited at the lecture. I have not reproduced them

here, because their likeness to the actual molecules is not appreciably greater

than that of Fig. u.

Q}tantum-Mechanical Evidence 59

energy. The state of affairs is sometimes figuratively pictured

as in Fig. 12, in which r and 2 represent the two isomeres, 3 the

'threshold' between them, and the two arrows indicate the

'lifts', that is to say, the energy supplies required to produce the

transition from state r to state 2 or from state 2 to state r,

respectively.

Now we can give our 'second amendment', which is that

transitions of this 'isomeric' kind are the only ones in which

we shall be interested in our biological application. It was these

we had in mind when explaining 'stability' on pp. 53-5. The

'quantum jump' which we mean is the transition from one

relatively stable molecular configuration to another. The energy

supply required for the transition ( the quantity denoted by W)

is not the actual level difference, but the step from the initial

level up to the threshold (see the arrows in Fig. 12).

Transitions with no threshold interposed between the initial

and the final state are entirely uninteresting, and that not only

in our biological application. They have actually nothing to

contribute to the chemical stability of the molecule. vVhy?

They have no lasting effect, they remain unnoticed. For, when

they occur, they are almost immediately followed by a relapse

into the initial state, since nothing prevents their return.

CHAPTER 5

DELBRUCK'S l\10DEL DISCUSSED

AND TESTED

Sane sicut lux seipsam et tenebras manifestat, sic yeritas norma sui et falsi est.1

SPINOZA, Ethics, Pt 11, Prop. 43.

THE GENERAL PICTURE OF THE HEREDITARY

SUBSTANCE

From these facts emerges a very simple answer to our question,

namely: Are these structures, composed of comparatively few

atoms, capable of withstanding for long periods the disturbing

influence of heat motion to which the hereditary substance is

continually exposed ? We shall assume the structure of a gene to

be that of a huge molecule, capable only of discontinuous change,

which consists in a rearrangement of the atoms and leads to an

isomeric2 molecule. The rearrangement may affect only a small

region of the gene, and a vast number of different rearrangements

may be possible. The energy thresholds, separating the

actual configuration from any possible isomeric ones, have to be

high enough ( compared with the average heat energy of an

atom) to make the change-over a rare event. These rare events

we shall identify with spontaneous mutations.

The later parts of this chapter will be devoted to putting this

general picture of a gene and of mutation ( due mainly to the

German physicist M. Delbrtick) to the test, by comparing it in

detail with genetical facts. Before doing so, we may fittingly

make some comment on the foundation and general nature of

the theory.

1 Truly, as light manifests itself and darkness, thus truth is the standard of itself

and of error.

2 For convenience I shall continue to call it an isomeric transition, though it would

be absurd to exclude the possibility of any exchange with the environment.

Delhrilck'Ms ode/Discusseadn d Tested 61

THE UNIQUENESS OF THE PICTURE

Was it absolutely c~ssentiaflo r the biologicalq uestion to dig up the

deepest roots and found the !picture on quantum mechanics?

The conjecture that a gene is a molecule is today, I dare say, a

commonplace. Fc~w biologists~ whether familiar with quantum

theory or not, would disagree with it. On p. 50 we ventured to

put it into the mouth of a pre-quantum physicist, as the only

reasonable explanation of the observed permanence. The subsequent

con.siderations about isomerism, threshold energy, the

paramount role of the ratio W: kT in determining the probability

ofan isome:ric transition-all that could very well be introduced

on a purely empirical basis, at any rate without drawing on

quantum theory. Why did I so strongly insist on the quantummechanical

point of view, though I could not really make it clear

in this little book and may well have bored many a reader ?

Q!iantum mechanics is the first theoretical aspect which

accounts from first principles for all kinds of aggregates of

atoms actually encountered in Nature. The Heider-London

bondage is a unique, singular feature of the theory, not invented

for the purpose of explaining the chemical bond. It comes in

quite by itself, in a highly interesting and puzzling manner,

being forced upon us by entirely different considerations. It

proves to correspond exactly with the observed chemical facts,

and,, as I said, it is a unique feature, well enough understood to

tell with reasonable certainty that 'such a thing could not

happen again' in. the further development of quantum theory.

Consequently, we may safely assert that there is no alternative

to the molecular explanation of the hereditary substance.

The physical aspect leaves no other possibility to

account fot its permanence. If the Delbriick picture should

fail, we would have to give up further attempts. That is the

first point I wish to make.

62 What is Life?

SOME TRADITIONAL MISCONCEPTIONS

But it may be asked: Are there really no other endurable

structures composed of atoms except molecules ? Does not a

gold coin, for example, buried in a tomb for a couple of thousand

years, preserve the traits of the portrait stamped on it? It is true

that the coin consists of an enormous number of atoms, but

surely we are in this case not inclined to attribute the mere

preservation of shape to the statistics of large numbers. The

same remark applies to a neatly developed batch of crystals we

find embedded in a rock, where it must have been for geological

periods without changing.

That leads us to the second point I want to elucidate. The

cases of a molecule, a solid, a crystal are not really different.

In the light of present knowledge they are virtually the same.

Unfortunately, school teaching keeps up certain traditional

views, which have been out of date for inany years and which

obscure the understanding of the actual state of affairs.

Indeed, what we have learnt at school about molecules does

not give the idea that they are more closely akin to the solid

state than to the liquid or gaseous state. On the contrary, we

have been taught to distinguish carefully between a physical

change, such as melting or evaporation in which the molecules

are preserved (so that, for example, alcohol, whether solid,

liquid or a gas, always consists of the same molecules, C2H60),

and a chemical change, as, for example, the burning of alcohol,

C2H60 + 30 2 = 2C0 2 + 3H20,

where an alcohol molecule and three oxygen molecules undergo

a rearrangement to form two molecules of carbon dioxide and

three molecules of water.

About crystals, we have been taught that they form threefold

periodic lattices, in which the structure of the single

Delbruck'sM odel Discusseda nd Tested 63

molecule is sometimes recognizable, as in the case of alcohol

and most organic compounds, while in other crystals, e.g.

rock-salt (NaCl), NaCl molecules cannot be unequivocally delimited,

because every Na atom is symmetrically surrounded by

six Cl atoms, and vice versa, so that it is largely arbitrary what

pairs, if any, are regarded as molecular partners.

Finally, we have been told that a solid can be crystalline or

not, and in the latter case we call it amorphous.

DIFFERENT 'STATES' OF MATTER

Now I would not go so far as to say that all these statements and

distinctions are quite wrong. For practical purposes they are

sometimes useful. But in the true aspect of the structure of

matter the limits must be drawn in an entirely different way.

The fundamental distinction is between the two lines of the

following scheme of' equations':

molecule = solid = crystal.

gas = liquid = amorphous.

We must explain these statements briefly. The so-called

amorphous solids are either not really amorphous or not really

solid. In 'amorphous' charcoal fibre the rudimentary structure

of the graphite crystal has been disclosed by X-rays. So

charcoal is a solid, but also crystalline. Where we find no

crystalline structure we have to regard the thing as a liquid

with very high 'viscosity' (internal friction). Such a substance

discloses by the absence of a well-defined melting temperature

and of a latent heat of melting that it is not a true solid. When

heated it softens gradually and eventually liquefies without discontinuity.

(I remember that at the end of the first Great War

we were given in Vienna an asphalt-like substance as a substitute

for coffee. It was so hard that one had to use a chisel or a

hatchet to break the little brick into pieces, when it would show

What is Life?

a smooth, shell-like cleavage. Yet, given time, it would behave

as a liquid, closely packing the lower part of a vessel in which

you were unwise enough to leave it for a couple of days.)

The continuity of the gaseous and liquid state is a wellknown

story. You can liquefy any gas without discontinuity by

taking your way 'around, the so-called critical point. But we

shall not enter on this here.

THE DISTINCTION THAT REALLY MATTERS

We have thus justified everything in the above scheme, except

the main point, namely, that we wish a molecule to be regarded

as a solid = crystal.

The reason for this is that the atoms forming a molecule,

whether there be few or many of them, are united by forces of

exactly the same nature as the numerous atoms which build up a

true solid, a crystal. The molecule presents the same solidity

of structure as a crystal. Remember that it is precisely this

solidity on which we draw to account for the permanence of the

gene!

The distinction that is really important in the structure of

matter is whether atoms are bound together by those 'solidifying'

Heider-London forces or whetl1er they are not. In a solid

and in a molecule they all are. In a gas of single atoms (as e.g.

mercury vapour) they are not. In a gas composed of molecules,

only the atoms within every molecule are linked in this way.

THE APERIODIC SOLID

A small molecule might be called 'the germ of a solid'. Starting

from such a small solid germ, there seem to be two different

ways of building up larger and larger associations. One is the

comparatively dull way of repeating the same structure in three

directions again and again. That is the way followed in a growDelbriick'sM

odel Discusseda nd Tested 65

ing crystal. Once the periodicity is established, there is no

definite limit to the size of the aggregate. The other way is that

of building up a more and more extended aggregate without the

dull device of repetition. That is the case of the more and more

complicated organic molecule in which every atom, and every

group of atoms, plays an individual role, not entirely equivalent

to that of many others (as is the case in a periodic structure).

We might quite properly call that an aperiodic crystal or solid

and express: our hypothesis qy saying: We believe a gene-o~

perhaps the wholi~ chromosome fibre1-to be an aperiodic solid.

THE VARIETY OF CONTENTS COMPRESSED

IN THE MINIATURE CODE

It has often been asked how this tiny speck of material, the

nucleus of the fertilized egg, could contain an elaborate codescript

involving all the future development of the organism. A

well-ordered association of atoms, endowed with sufficient

resistivity to keep its order permanently, appears to be the only

conceivable material structure that offers a variety of possible

('isomeric') arrangements, sufficiently large to embody a complicated

system of 'determinations' within a small spatial

boundary. Indeed, the number of atoms in such a structure

need not be very large to produce an almost unlimited number

of possible arrangements. For illustration, think of the Morse

code. The two different signs of dot and dash in well-ordered

groups of not mo:re than four allow of thirty different specifications.

Now, if you allowed yourself the use of a third sign, in

addition to dot and dash, and used groups of not more than ten,

you could form 88,572 different 'letters'; with five signs and

groups up t:o 25, the number is 372,529,029,846,191,405.

It may be objected that the simile is deficient, because our

1 That it is highly flexible is no objection; so is a thin copper wire.

66 What is Life?

Morse signs may have different composition (e.g. •--and••-)

and thus they are a bad analogue for isomerism. To remedy

this defect, let us pick, from the third example, only the combinations

of exactly 25 symbols and only those containing

exactly 5 out of each of the supposed 5 types (5 dots, 5 dashes,

etc.). A rough count gives you the number of combinations as

62,330,000,ooo,ooo, where the zeros on the right stand for

figures which I have not taken the trouble to compute.

Of course, in the actual case, by no means 'every' arrangement

of the group of atoms will represent a possible molecule;

moreover, it is not a question of a code to be adopted arbitrarily,

for the code-script must itself be the operative factor bringing

about the development. But, on the other hand, the number

chosen in the example (25) is still very small, and we have envisaged

only the simple arrangements in one line. What we

wish to illustrate is simply that with the molecular picture of the

gene it is no longer inconceivable that the miniature code should

precisely correspond with a highly complicated and specified

plan of development and should somehow contain the means to

put it into operation.

COMPARISON WITH FACTS: DEGREE OF STABILITY;

DISCONTINUITY OF MUTATIONS

Now let us at last proceed to compare the theoretical picture

with the biological facts. The first question obviously is,

whether it can really account for the high degree of permanence

we observe. Are threshold values of the required amounthigh

multiples of the average heat energy kT-reasonable, are

they within the range known from ordinary chemistry? That

question is trivial; it can be answered in the affirmative without

inspecting tables. The molecules of any substance which the

chemist is able to isolate at a given temperature must at that

Delbriick's Model Discussed and Tested 67

temperature have a lifetime of at least minutes. (That is putting

it mildly; as a rule they have much more.) Thus the threshold

values the chemist encounters are of necessity precisely of the

order of magnitude required to account for practically any

degree of permanence the biologist may encounter; for we

recall from p. 55 that thresholds varying within a range of

about 1 : 2 will account for lifetimes ranging from a fraction of a

second to tens of thousands of years.

But let me mention figures, for future reference. The ratios

W/kT mentioned by way of example on p. 55, viz.

w

kT = 30, 50, 60,

producing lifetimes of

lo s., 16 months, 30,000 years,

respectively, correspond at room temperature with threshold

values of 0·9, 1 • 5, 1 ·8 electron-volts.

We must explain the unit 'electron-volt', which is rather convenient

for the physicist, because it can be visualized. For

example, the third number (1·8) means that an electron, accelerated

by a voltage of about 2 volts, would have acquired just

sufficient energy to effect the transition by impact. (For comparison,

the battery of an ordinary pocket flash-light has

3 volts.)

These considerations make it conceivable that an isomeric

change of configuration in some part of our molecule, produced

by a chance fluctuation of the vibrational energy, can actually

be a sufficiently rare event to be interpreted as a spontaneous

mutation. Thus we account, by the very principles of quantum

mechanics, for the most amazing fact about mutations, the fact

by which they first attracted de Vries's attention, namely, that

they are 'jumping' variations~ no intermediate forms occurring.

68 What is Life .2

STABILITY OF NATURALLY SELECTED GENES

Having discovered the increase of the natural mutation rate

by any kind of ionizing rays, one might think of attributing

the natural rate to the radio-activity of the soil and air and

to cosmic radiation. But a quantitative comparison with the

X-ray results shows that the 'natural radiation' is much too

weak and could account only for a small fraction of the natural

rate.

Granted that we have to account for the rare natural mutations

by chance fluctuations of the heat motion, we must not

be very much astonished that Nature has succeeded in making

such a subtle choice of threshold values as is necessary to make

mutation rare. For we have, earlier in these lectures, arrived at

the conclusion that frequent mutations are detrimental to

evolution. Individuals which, by mutation, acquire a gene configuration

of insufficient stability, will have little chance of

seeing their 'ultra-radical', rapidly mutating descendancy survive

long. The species will be freed of them and will thus collect

stable genes by natural selection.

THE SOMETIMES LOWER STABILITY OF MUTANTS

But, of course, as regards the mutants which occur in our

breeding experiments and which we select, qua mutants, for

studying their offspring, there is no reason to expect that they

should all show that very high stability. For they have not yet

been 'tried out '-or, if they have, they have been 'rejected'

in the wild breeds-possibly for too high mutability. At any

rate, we are not at all astonished to learn that actually some of

these mutants do show a much higher mutability than the

normal 'wild' genes.

Delbrack'sM odelD iscusseda nd Tested 69

TEMPERATURE INFLUENCES UNSTABLE GENES

LESS THAN ST ABLE ONES

This enabfos us to test our mutability formula, which was

t = -reW/kT,

(It will be remembered that t is the time of expectation for a

mutation with threshold energy W.) We ask: How does t change

with the temperature ? We easily find from the preceding formula

in good approximation the ratio of the value of t at

temperature T -1-10 to that at temperature T

fT+lO = elOWikT 2 ,

tT

The exponent being now negative, the ratio is, naturally,

smaller than I. The time of expectation is diminished by raising

the temperature 1, the mutability is increased. Now that can be

tested and has been tested with the fly Drosophilai n the range

of temperature which the insects will stand. The result was, at

first sight, surprising. The low mutability of wild genes was

distinctly increased, but the comparatively high mutability

occurring with some of the already mutated genes was not, or at

any rate was much less, increased. That is just what we expect

on comparing our two formulae. A large value of W/ kT, which

according to the first formula is required to make t large (stable

gene), will~ according to the second one, make for a small value

of the ratio computed there, that is to say for a considerable

increase of mutability with temperature. (The actual values of

the ratio seem to lie between aboutó and.- The reciprocal, 2·5,

is what in an ordinary chemical reaction we call the van 't Hoff

factor.)

What is Life?

HOW X-RAYS PRODUCE MUTATION

Turning now to the X-ray-induced mutation rate, we have

already inferred from the breeding experiments, first (from the

proportionality of mutation rate, and dosage), that some single

event produces the mutation; secondly (from quantitative

results and from the fact that the mutation rate is determined by

the integrated ionization density and independent of the wavelength),

that this single event must be an ionization, or similar

process, which has to take place inside a certain volume of only

about ro atomic-distances-cubed, in order to produce a specified

mutation. According to our picture, the energy for overcoming

the threshold must obviously be furnished by that explosionlike

process, ionization or excitation. I call it explosion-like,

because the energy spent in one ionization (spent, incidentally,

not by the X-ray itself, but by a secondary electron it produces)

is well known and has the comparatively enormous amount of

30 electron-volts. It is bound to be turned into enormously increased

heat motion around the point where it is discharged and

to spread from there in the form of a' heatwave', a wave ofintense

oscillations of the atoms. That this heat wave should still be

able to furnish the required threshold energy of r or 2 electronvolts

at an average 'range of action' of about ten atomic distances,

is not inconceivable, though it may well be that an unprejudiced

physicist might have anticipated a slightly lower

range of action. That in many cases the effect of the explosion

will not be an orderly isomeric transition but a lesion of the

chromosome, a lesion that becomes lethal when, by ingenious

crossings, the uninjured partner ( the corresponding chromosome

of the second set) is removed and replaced by a partner

whose corresponding gene is known to be itself morbid-all that

is absolutely to be expected and it is exactly what is observed.

Delbruck'sM odel Discusseda nd Tested 71

THEIR EFFICIENCY DOES NOT DEPEND

ON SPONTANEOUS MUTABILITY

Qyite a few other features are, if not predictable from the

picture, easily understood from it. For example, an unstable

mutant does not on the average show a much higher X-ray

mutation rate than a stable one. Now, with an explosion furnishing

an energy of 30 electron-volts you would certainly not

expect that it makes a lot of difference whether the required

threshold energy is a little larger or a little smaller, say I or

1·3 volts.

REVERSIBLE MUTATIONS

In some cases a transition was studied in both directions, say

from a certain 'wild' gene to a specified mutant and back from

that mutant to the wild gene. In such cases the natural mutation

rate is sometimes nearly the same, sometimes very different. At

first sight one is puzzled, because the threshold to be overcome

seems to be the same in both cases. But, of course, it need not be,

because it has to be measured from the energy level of the

starting configuration, and that may be different for the wild

and the mutated gene. (See Fig. 12 on p. 58, where '1' might

refer to the wild allele, '2' to the mutant, whose lower stability

would be indicated by the shorter arrow.)

On the whole, I think, Delbriick's 'model' stands the tests

fairly well and we are justified in using it in further considerations.

CHAPTER 6

ORDER, DISORDER AND ENTROPY

Nee corpus mentem ad cogitandum nee mens corpus ad motwn, neque ad

quietem nee ad aliquid (si quid est) aliud determinare potest.1

SPINOZA, Ethics, Pt m, Prop. :.i

A REMARKABLE GENERAL CONCLUSION

FROM THE MODEL

Let me refer to the phrase on p. 66, in which I tried to explain

that the molecular picture of the gene made it at least conceivable

that the miniature code should be in one-to-one

correspondence with a highly complicated and specified plan of

development and should somehow contain the means of putting

it into operation. Very well then, but how does it do this ?

How are we going to turn 'conceivability' into true understanding?

Delbriick's molecular model, in its complete generality,

seems to contain no hint as to how the hereditary substance

works. Indeed, I do not expect that any detailed information

on this question is likely to come from physics in the near

future. The advance is proceeding and will, I am sure, continue

to do so, from biochemistry under the guidance of physiology

and genetics.

No detailed information about the functioning of the genetical

mechanism can emerge from a description of its structure so

general as has been given above. That is obvious. But, strangely

enough, there is just one general conclusion to be obtained from

it, and that, I confess, was my only motive for writing this

book.

1 Neither can the body determine the mind to think, nor the mind determine

the body to motion or rest or anything else (if such there be).

Order,D iso-rdearn d Entropy 73

From Delbrikk's general picture of the hereditary substance

it emerges that living matter, while not eluding the 'laws of

physics' as established up to date, is likely to involve '0th.er

laws of physics' hitherto unknown, which, however, once they

have been reveafod, will form just as integral a part of this science

as the former.

ORDER BASED ON ORDER

This is a rather subtle line of thought, open to misconception

in more than one respect. All the remaining pages are concerned

with making it dear. A preliminary insight, rough but not altogether

erroneous, may be found in the following considerations:

It has been explained in chapter I that the laws of physics, as

we know them, are statistical laws.1 They have a lot to do with

the natural tendency of things to go over into disorder.

But, to reconc:ile the high durability of the hereditary substance

with its minute size, we had to evade the tendency to

disorder by 'imrenting the :molecule', in fact, an unusually

large molecule which has to be a masterpiece of highly differentiated

order, safeguarded by the conjuring rod of quantum

theory. The laws of chance are not invalidated by this 'invention',

but their outcome is modified. The physicist is familiar

with the fact that the classical laws of physics are modified by

quantum theory, especially at low temperature. There are many

instances of this. Life seems to be one of them, a particularly

striking one. Life seems to be orderly and lawful behaviour of

matter, not based exclusively on its tendency to go over from

order to disorder, but based partly on existing order that is

kept up.

To the physicist-but only to him-I could hope to make

my view clearer by saying: The living organism seems to be a

1 To state this in complete generality about 'the laws of physics' is perhaps

challengeable. The point will be discussed in chapter 7.

74 What is Life?

macroscopic system which in part of its behaviour approaches

to that purely mechanical ( as contrasted with thermodynamical)

conduct to which all systems tend, as the temperature approaches

the absolute zero and the molecular disorder is

removed.

The non-physicist finds it hard to believe that really the

ordinary laws of physics, which he regards as the prototype of

inviolable precision, should be based on the statistical tendency

of matter to go over into disorder. I have given examples in

chapter 1. The general principle involved is the famous

Second Law of Thermodynamics (entropy principle) and its

equally famous statistical foundation. On pp. 73-9 I will try

to sketch the bearing of the entropy principle on the large-scale

behaviour of a living organism-forgetting at the moment all

that is known about chromosomes, inheritance, and so on.

LIVING MATTER EVADES THE DECAY TO EQUILIBRIUM

What is the characteristic feature of life ? When is a piece of

matter said to be alive ? When it goes on 'doing something',

moving, exchanging material with its environment, and so

forth, and that for a much longer period than we would expect

an inanimate piece of matter to 'keep going' under similar

circumstances. When a system that is not alive is isolated or

placed in a uniform environment, all motion usually comes to a

standstill very soon as a result of various kinds of friction;

differences of electric or chemical potential are equalized,

substances which tend to form a chemical compound do so,

temperature becomes uniform by heat conduction. After that

the whole system fades away into a dead, inert lump of matter. A

permanent state is reached, in which no observable events occur.

The physicist calls this the state of thermodynamical equilibrium,

or of' maximum entropy'.

Order, Disorder and Entropy 75

Practically, a state of this kind is usually reached very rapidly.

Theoretically, it is very often not yet an absolute equilibrium,

not yet the true maximum of entropy. But then the final

approach to equilibrium is very slow. It could take anything

between hours, years, centuries, ... To give an example-one

in which the approach is still fairly rapid: if a glass filled with

pure water and a second one filled with sugared water are placed

together in a hermetically closed case at constant temperature, it

appears at first that nothing happens, and the impression of

complete equilibrium is created. But after a day or so it is

noticed that the pure water, owing to its higher vapour pressure,

slowly evaporates and condenses on the solution. The latter

overflows. Only after the pure water has totally evaporated has

the sugar reached its aim of being equally distributed among all

the liquid water available.

These ultimate slow approaches to equilibrium could never

be mistaken for life, and we may disregard them here. I have

ref erred to them in order to clear myself of a charge of inaccuracy.

IT FEEDS ON 'NEGATIVE ENTROPY'

It is by avoiding the rapid decay into the inert state of 'equilibrium'

that an organism appears so enigmatic; so much so, that

from the earliest times of human thought some special nonphysical

or supernatural force (vis viva, entelechy) was claimed

to be operative in the organism, and in some quarters is still

claimed.

How does the living organism avoid decay? The obvious

answer is: By eating, drinking, breathing and (in the case of

plants) assimilating. The technical term is metabolism. The

Greek word (p,E:-ra{3aA.>m-e.Ean:ws )c hange or exchange. Exchange

of what? Originally the underlying idea is, no doubt,

exchange of material. (E.g. the German for metabolism is

What is Life .2

Stoffwechsel.) That the exchange of material should be the

essential thing is absurd. Any atom of nitrogen, oxygen, sulphur,

etc., is as good as any other of its kind; what could be gained by

exchanging them? For a while in the past our curiosity was

silenced by being told that we feed upon energy. In some very

advanced country (I don't remember whether it was Germany

or the U.S.A. or both) you could find menu cards in restaurants

indicating, in addition to the price, the energy content of every

dish. Needless to say, taken literally, this is just as absurd. For

an adult organism the energy content is as stationary as the

material content. Since, surely, any calorie is worth as much as any

other calorie, one cannot see how a mere exchange could help.

What then is that precious something contained in our food

which keeps us from death? That is easily answered. Every

process, event, happening-call it what you will; in a word,

everything that is going on in Nature means an increase of the

entropy of the part of the world where it is going on. Thus a

living organism continually increases its entropy-or, as you

may say, produces positive entropy-and thus tends to approach

the dangerous state of maximum entropy, which is

death. It can only keep aloof from it, i.e. alive, by continually

drawing from its environment negative entropy-which is

something very positive as we shall immediately see. What an

organism feeds upon is negative entropy. Or, to put it less paradoxically,

the essential thing in metabolism is that the organism

succeeds in freeing itself from all the entropy it cannot help

producing while alive.

WHAT IS ENTROPY?

What is entropy? Let me first emphasize that it is not a hazy

concept or idea, but a measurable physical quantity just like the

length of a rod, the temperature at any point of a body, the heat

Order, Disorder and Entropy 77

of fusion of a giv,en crystal or the specific heat of any given substance.

At the a.bsolute zero point of temperature (roughly

- 273 °C) the entropy of any substance is zero. When you bring

the substance into any other state by slow, reversible little steps

(even ifthereby the substanc,e changes its physical or chemical

nature or splits up into two or more parts of different physical

or chemical nature) the entropy increases by an amount which

is computed by dividing every little portion of heat you had to

supply in that procedure by the absolute temperature at which

it was supplied--and by summing up all these small contributions.

To give an example, when you melt a solid, its entropy

increases hy the amount of the heat of fusion divided by the

temperature at the melting-point. You see from this, that the

unit in which entropy is measured is cal./°C (just as the calorie

is the unit of hea.t or the centimetre the unit of length).

THE STATISTICAL MEANING OF ENTROPY

I have mentioned this technical definition simply in order to

remove entropy from the atmosphere of hazy mystery that frequently

veils it. Much more important for us here is the

bearing on the statistical concept of order and disorder, a connection

that was revealed by the investigations of Boltzmann

and Gibbs in statistical physics. This too is an exact quantitative

connection, and is express by

entropy = k log D,

where k is the so-called Boltzmann constant ( = 3·2983. ro- 24

cal./°C), and D a quantitative measure of the atomistic disorder

of the body in question. To give an exact explanation of this

quantity D in brief non-technical terms is well-nigh impossible.

The disorder it indicates is partly that of heat motion, partly

that which consists in different kinds of atoms or molecules

being mixed at random, instead of being neatly separated, e.g.

What is Life .2

the sugar and water molecules in the example quoted above.

Boltzmann's equation is well illustrated by that example. The

gradual 'spreading out' of the sugar over all the water available

increases the disorder D, and hence (since the logarithm of D

increases with D) the entropy. It is also pretty clear that any

supply of heat increases the turmoil of heat motion, that is to

say, increases D and thus increases the entropy; it is particularly

clear that this should be so when you melt a crystal, since you

thereby destroy the neat and permanent arrangement of the

atoms or molecules and turn the crystal lattice into a continually

changing random distribution.

An isolated system or a system in a uniform environment

(which for the present consideration we do best to include as a

part of the system we contemplate) increases its entropy and

more or less rapidly approaches the inert state of maximum

entropy. We now recognize this fundamental law of physics

to be just the natural tendency of things to approach the chaotic

state ( the same tendency that the books of a library or the piles

of papers and manuscripts on a writing desk display) unless we

obviate it. (The analogue of irregular heat motion, in this case,

is our handling those objects now and again without troubling

to put them back in their proper places.)

ORGANIZATION MAINTAINED BY EXTRACTING

'ORDER' FROM THE ENVIRONMENT

How would we express in terms of the statistical theory the

marvellous faculty of a living organism, by which it delays the

decay into thermodynamical equilibrium ( death) ? We said

before: 'It feeds upon negative entropy', attracting, as it were,

a stream of negative entropy upon itself, to compensate the

entropy increase it produces by living and thus to maintain

itself on a stationary and fairly low entropy level.

Order,D isordera nd Entropy 79

If D is a measure of disorder, its reciprocal, 1/D, can be

regarded as a direct measure of order. Since the logarithm of

1/D is just minus the logarithm of D, we can write Boltzmann's

equation thus: _ (entropy) = k log (r/D).

Hence the awkward expression 'negative entropy' can be replaced

by a better one: entropy, taken with the negative sign,

is itself a measure of order. Thus the device by which an

organism maintains itself stationary at a fairly high level of

orderliness ( = fairly low level of entropy) really consists in

continually sucking orderliness from its environment. This

conclusion is less paradoxical than it appears at first sight.

Rather could it be blamed for triviality. Indeed, in the case of

higher animals we know the kind of orderliness they feed upon

well enough, viz. the extremely well-ordered state of matter in

more or less complicated organic compounds, which serve them

as foodstuffs. After utilizing it they return it in a very much

degraded form-not entirely degraded, however, for plants can

still make use of it. (These, of course, have their most powerful

supply of 'negative entropy' in the sunlight.)

NOTE TO CHAPTER 6

The remarks on negative entropy have met with doubt and opposition

from physicist colleagues. Let me say first, that ifl had been catering

for them alone I should have let the discussion turn on free energy

instead. It is the more familiar notion in this context. But this highly

technical term seemed linguistically too near to energy for making the

average reader alive to the contrast between the two things. He is

likely to take free as more or less an epitheton ornans without much

relevance, while actually the concept is a rather intricate one, whose

relation to Boltzmann's order-disorder principle is less easy to trace

than for entropy and 'entropy taken with a negative sign', which by

the way is not my invention. It happens to be precisely the thing on ){

which Boltzmann's original argument turned.

80 What is Life .2

But F. Simon has very pertinently pointed out to me that my simple

thermodynamical considerations cannot account for our having to

feed on matter 'in the extremely well ordered state of more or less

complicated organic compounds' rather than on charcoal or diamond

pulp. He is right. But to the lay reader I must explain that a piece of

un-burnt coal or diamond, together with the amount of oxygen

needed for its combustion, is also in an extremely well ordered state,

as the physicist understands it. Witness to this: if you allow the

reaction, the burning of the coal, to take place, a great amount of heat

is produced. By giving it off to the surroundings, the system disposes

of the very considerable entropy increase entailed by the reaction,

and reaches a state in which it has, in point of fact, roughly the same

entropy as before.

Yet we could not feed on the carbon dioxide that results from the

reaction. And so Simon is quite right in pointing out to me, as he did,

that actually the energy content of our food does matter; so my

mocking at the menu cards that indicate it was out of place. Energy is

needed to replace not only the mechanical energy of our bodily

exertions, but also the heat we continually give off to the environment.

And that we give off heat is not accidental, but essential. For

this is precisely the manner in which we dispose of the surplus

entropy we continually produce in our physical life process.

This seems to suggest that the higher temperature of the warmblooded

animal includes the advantage of enabling it to get rid of its

entropy at a quicker rate, so that it can afford a more intense life process.

I am not sure how much truth there is in this argument (for

which I am responsible, not Simon). One may hold against it, that on

the other hand many warm-blooders are protected against the rapid

loss of heat by coats of fur or feathers. So the parallelism between body

temperature and 'intensity of life', which I believe to exist, may

have to be accounted for more directly by van 't Hoff's law, mentioned

on p. 69: the higher temperature itself speeds up the chemical

reactions involved in living. (That it actually does, has been confirmed

experimentally in species which take the temperature of the

surrounding.)

CHAPTER 7

IS LIFE BASED ON THE LAWS

OF PHYSICS?

Si un hombre 11unca se contradice, sera porque nunca dice nada.1

MIGUEL D~ UNAMUNO (quoted from conversation)

NEW LAWS TO BE EXPECTED IN THE ORGANISM

What I wish to make clear in this last chapter is, in short, that

from all we have learnt about the structure of living matter, we

must be prepared to find it working in a manner that cannot be

reduced to the ordinary laws of physics. And that not on the

ground that there is any 'new force' or what not, directing the

behaviour of the single atoms within a living organism, but

because the. construction is different from anything we have

yet tested in the physical laboratory. To put it crudely, an

engineer, familiar with heat engines only, will, after inspecting

the construction of an electric motor, be prepared to find it

working along principles which he does not yet understand.

He finds the copper familiar to him in kettles used here in the

form oflong, long: wires wound in coils; the iron familiar to him

in levers and bars and steam cylinders is here filling the interior

of those coils of copper wire. He will be convinced that it is the

same copper and the same iron, subject to the same laws of

Nature, and he is right in that. The difference in construction is

enough to prepare him for an entirely different way of functioning.

He will not :suspect that an electric motor is driven by a

ghost because it is set spinning by the turn of a switch, without

boiler and steam.

1 If a man never contradicts himself, the reason must be that he virtually never

says anything at all

82 What is Life?

REVIEWING THE BIOLOGICAL SITUATION

The unfolding of events in the life cycle of an organism exhibits

an admirable regularity and orderliness, unrivalled by anything

we meet with in inanimate matter. We find it controlled by a

supremely well-ordered group of atoms, which represent only a

very small fraction of the sum total in every cell. Moreover, from

the view we have formed of the mechanism of mutation we conclude

that the dislocation of just a few atoms within the group of

'governing atoms' of the germ cell suffices to bring about a welldefined

change in the large-scale hereditary characteristics of

the organism.

These facts are easily the most interesting that science has

revealed in our day. We may be inclined to find them, after all,

not wholly unacceptable. An organism's astonishing gift of

concentrating a 'stream of order' on itself and thus escaping

. .. the decay into atomic chaos-of ' drinking orderliness' from a

suitable environment-seems to be connected with the presence

of the 'aperiodic solids', the chromosome molecules,

which doubtless represent the highest degree of well-ordered

atomic association we know of.-much higher than the ordinary

periodic crystal-in virtue of the individual role every atom

and every radical is playing here.

To put it briefly, we witness the event that existing order

displays the power of maintaining itself and of producing

orderly events. That sounds plausible enough, though in

finding it plausible we, no doubt, draw on experience concerning

social organization and other events which involve the

activity of organisms. And so it might seem that something like

a vicious circle is implied.

Is Life Based on the Laws of Physics? 83

SUMMARIZING THE PHYSICAL SITUATION

However that may be, the point to emphasize again and again

is that to the physicist the state of affairs is not only not plausible

but most exciting, because it is unprecedented. Contrary

to the common belief, the regular course of events, governed by

the laws of physics, is never the consequence of one wellordered

configuration of atoms-not unless that configuration

of atoms repeats itself a great number of times, either as in the

periodic crystal or as in a liquid or in a gas composed of a great

number of identical molecules.

Even when the chemist handles a very complicated molecule

in vitro he is always faced with an enormous number of like

molecules. To them his laws apply. He might tell you, for

example, that one minute after he has started some particular

reaction half of the molecules will have reacted, and after a

second minute three-quarters of them will have done so. But

whether any particular molecule, supposing you could follow

its course, will be among those which have reacted or among

those which are still untouched, he could not predict. That is

a matter of pure chance.

This is not a purely theoretical conjecture. It is not that we

can never observe the fate of a single small group of atoms or

even of a single atom. We can, occasionally. But whenever we

do, we find complete irregularity, co-operating to produce

regularity only on the average. We have dealt with an example

in chapter 1. The Brownian movement of a small particle suspended

in a liquid is completely irregular. But if there are many

similar particles, they will by their irregular movement give

rise to the regular phenomenon of diffusion.

The disintegration of a single radioactive atom is observable

(it emits a projectile which causes a visible scintillation on a

fluorescent screen). But if you are given a single radioactive

What is Life?

atom, its probable lifetime is much less certain than that of a

healthy sparrow. Indeed, nothing more can be said about it

than this: as long as it lives (and that may be for thousands of

years) the chance of its blowing up within the next second,

whether large or small, remains the same. This patent lack of

individual determination nevertheless results in the exact

exponential law of decay of a large number of radioactive

atoms of the same kind.

THE STRIKING CONTRAST

In biology we are faced with an entirely different situation. A

single group of atoms existing only in one copy produces orderly

events, marvellously tuned in with each other and with the

environment according to most subtle laws. I said, existing

only in one copy, for after all we have the example of the egg

and of the unicellular organism. In the following stages of a

higher organism the copies are multiplied, that is true. But to

what extent? Something like ro14 in a grown mammal, I understand.

What is that! Only a millionth of the number of molecules

in one cubic inch of air. Though comparatively bulky, by

coalescing they would form but a tiny drop of liquid. And look

at the way they are actually distributed. Every cell harbours

just one of them ( or two, if we bear in mind diploidy). Since we

know the power this tiny central office has in the isolated cell,

do they not resemble stations of local government dispersed

through the body, communicating with each other with great

ease, thanks to the code that is common to all of them ?

Well, this is a fantastic description, perhaps less becoming a

scientist than a poet. However, it needs no poetical imagination

but only clear and sober scientific reflection to recognize that

we are here obviously faced with events whose regular and

lawful unfolding is guided by a 'mechanism' entirely different

b Life Based on the Laws of Physics? 85

from the 'probability mechanism' of physics. For it is simply a

fact of observation that the guiding principle in every cell is

embodied in a single atomic association existing only in one

copy ( or sometimes two )-and a fact of observation that it

results in producing events which are a paragon of orderliness.

Whether we: find it astonishing or whether we find it quite

plausible that a small but highly organized group of atoms be

capable of acting in this manner, the situation is unprecedented,

it is unknown anywhere else except in living matter. The

physicist and th,~ chemist, investigating inanimate matter,

have never witnessed phenomena which they had to interpret

in this way. The case did not arise and so our theory

does not cover it--our beautiful statistical theory of which we

were so justly proud because it allowed us to look behind the

curtain, to watch the magnificent order of exact physical law

coming forth from atomic and molecular disorder; because it

revealed that the most impmtant, the most general, the allembracing

law of entropy increase could be understood without

a special assumption ad hoc, for it is nothing but molecular

disorder itself.

TWO WAYS OF PRODUCING ORDERLINESS

The orderliness encountered in the unfolding of life springs

from a different source. It appears that there are two different

'mechanisms' by which orderly events can be produced: the

'statistical mechanism' which produces 'order from disorder'

and the new one, producing 'order from order'. To the unprejudiced

mind the second principle appears to be much simpler,

much more plausible. No doubt it is. That is why physicists

were so proud to have fallen in with the other one, the 'orderfrom-

disorder' principle, which is actually followed in Nature

and which alone conveys an understanding of the great line of

86 What is Life?

natural events, in the first place of their irreversibility. But we

cannot expect that the 'laws of physics' derived from it suffice

straightaway to explain the behaviour of living matter, whose

most striking features are visibly based to a large extent on the

'order-from-order' principle. You would not expect two entirely

different mechanisms to bring about the same type oflaw

-you would not expect your latch-key to open your neighbour's

door as well.

We must therefore not be discouraged by the difficulty of

interpreting life by the ordinary laws of physics. For that is

just what is to be expected from the knowledge we have gained

of the structure ofliving matter. We must be prepared to find a

new type of physical law prevailing in it. Or are we to term it a

non-physical, not to say a super-physical, law?

THE NEW PRINCIPLE IS NOT ALIEN TO PHYSICS

No. I do not think that. For the new principle that is involved is

a genuinely physical one: it is, in my opinion, nothing else than

the principle of quantum theory over again. To explain this, we

have to go to some length, including a refinement, not to say an

amendment, of the assertion previously made, namely, that all

physical laws are based on statistics.

This assertion, made again and again, could not fail to arouse

contradiction. For, indeed, there are phenomena whose conspicuous

features are visibly based directly on the 'order-fromorder'

principle and appear to have nothing to do with statistics

or molecular disorder.

The order of the solar system, the motion of the planets, is

maintained for an almost indefinite time. The constellation of

this moment is directly connected with the constellation at

any particular moment in the times of the Pyramids; it can

be traced back to it, or vice versa. Historical eclipses have been

Is Life Based on the Laws of Physics? 87

calculated and have been found in close agreement with historical

records or have even in some cases served to correct the

accepted chronology. These calculations do not imply any

statistics, they are based solely on Newton's law of universal

attraction.

Nor does the regular motion of a good clock or of any similar

mechanism appear to have anything to do with statistics. In

short, all purely mechanical events seem to follow distinctly

and directly the 'order-from-order' principle. And if we say

'mechanical', the term must be taken in a wide sense. A very

useful kind of clock is, as you know, based on the regular

transmission of electric pulses from the power station.

I remember an interesting little paper by Max Planck on

the topic 'The Dynamical and the Statistical Type of Law'

(' Dynamische und Statistische Gesetzmassigkeit '). The distinction

is precisely the one we have here labelled as 'order

from order' and' order from disorder'. The object of that paper

was to show how the interesting statistical type of law, controlling

large-scale events, is constituted from the 'dynamical'

laws supposed to govern the small-scale events, the interaction

of the single atoms and molecules. The latter type is illustrated

by large-scale mechanical phenomena, as the motion of the

planets or of a clock, etc.

Thus it would appear that the 'new' principle, the orderfrom-

order principle, to which we have pointed with great

solemnity as being the real clue to the understanding of life,

is not at all new to physics. Planck's attitude even vindicates

priority for it. We seem to arrive at the ridiculous conclusion

that the clue to the understanding of life is that it is based on a

pure mechanism, a 'clock-work' in the sense of Planck's paper.

The conclusion is not ridiculous and is, in my opinion, not

entirely wrong, but it has to be taken 'with a very big grain of

salt'.

88 What is Life .2

THE MOTION OF A CLOCK

Let us analyse the motion of a real clock accurately. It is not at

all a purely mechanical phenomenon. A purely mechanical

clock would need no spring, no winding. Once set in motion,

it would go on for ever. A real clock without a spring stops after

a few beats of the pendulum, its mechanical energy is turned

into heat. This is an infinitely complicated atomistic process.

The general picture the physicist forms of it compels him to

admit that the inverse process is not entirely impossible: a

springless clock might suddenly begin to move, at the expense

of the heat energy of its own cog wheels and of the environment.

The physicist would have to say: The clock experiences an

exceptionally intense fit of Brownian movement. \Ve have seen

in chapter 2 (p. 17) that with a very sensitive torsional balance

( electrometer or galvanometer) that sort of thing happens all the

time. In the case of a clock it is, of course, infinitely unlikely.

Whether the motion of a clock is to be assigned to the dynamical

or to the statistical type oflawful events (to use Planck's

expressions) depends on our attitude. In calling it a dynamical

phenomenon we fix attention on the regular going that can be

secured by a comparatively weak spring, which overcomes the

small disturbances by heat motion, so that we may disregard

them. But if we remember that without a spring the clock is

gradually slowed down by friction, we find that this process

can only be understood as a statistical phenomenon.

However insignificant the frictional and heating effects in a

clock may be from the practical point of view, there can be no

doubt that the second attitude, which does not neglect them,

is the more fundamental one, even when we are faced with the

regular motion of a clock that is driven by a spring. For it must

not be believed that the driving mechanism really does away

·with the statistical nature of the process. The true physical

ls Life Based on the Laws of Physics? 89

picture includes the possibility that even a regularly going clock

should all at once invert its motion and, working backward, rewind

its own spring-at the expense of the heat of the environment.

The event is just' still a little less likely' than a' Brownian

fit' of a clock without driving mechanism.

CLOCKWORK AFTER ALL STATISTICAL

Let us now review the situation. The 'simple' case we have

analysed is representative of many others-in fact of all such

as appear to evade the all-embracing principle of molecular

statistics. Clockworks made of real physical matter (in contrast

to imagination) are not true 'clock-works'. The element

of chance may be more or less reduced, the likelihood of the

clock suddenly g:oing altogether wrong may be infinitesimal,

but it always remains in the background. Even in the motion

of the celestial bodies irreversible frictional and thermal influences

are not wanting. Thus the rotation of the earth is

slowly diminished by tidal friction, and along with this reduction

the moon gradually recedes from the earth, which would

not happen if the earth were a completely rigid rotating sphere.

Nevertheless the fact remains that 'physical clock-works'

visibly display very prominent 'order-from-order' featuresthe

type that aroused the physicist's excitement when he encountered

them in the organism. It seems likely that the two

cases have after all something in common. It remains to be seen

what this is and what is the striking difference which makes the

case of the organism after all novel and unprecedented.

NERNST 1S THEOREM

\Vhen does a physical system-any kind of association of atoms

-display' dynamical law' (in Planck's meaning) or' clock-work

features' ? Qpantum theory has a very short answer to this

4 SWI

90 What is Life?

question, viz. at the absolute zero of temperature. As zero

temperature is approached the molecular disorder ceases to

have any bearing on physical events. This fact was, by the

way, not discovered by theory, but by carefully investigating

chemical reactions over a wide range of temperatures and

extrapolating the results to zero temperature-which cannot

actually be reached. This is Walther Nernst's famous 'Heat

Theorem', which is sometimes, and not unduly, given the

proud name of the 'Third Law of Thermodynamics' ( the first

being the energy principle, the second the entropy principle).

Q!tantum theory provides the rational foundation ofNernst's

empirical law, and also enables us to estimate how closely a

system must approach to the absolute zero in order to display

an approximately' dynamical' behaviour. What temperature is

in any particular case already practically equivalent to zero ?

Now you must not believe that this always has to be a very

low temperature. Indeed, Nernst's discovery was induced by

the fact that even at room temperature entropy plays an

astonishingly insignificant role in many chemical reactions.

(Let me recall that entropy is a direct measure of molecular

disorder, viz. its logarithm.)

THE PENDULUM CLOCK IS VIRTUALLY AT

ZERO TEMPERATURE

What about a pendulum clock? For a pendulum clock room

temperature is practically equivalent to zero. That is the reason

why it works 'dynamically'. It will continue to work as it does

if you cool it (provided that you have removed all traces of oil!).

But it does not continue to work if you heat it above room

temperature, for it will eventually melt.

Is Life Based on the Laws of Physics? 91

THE RELATION BETWEEN CLOCKWORK

AND ORGANISM

That seems very trivial but it does, I think, hit the cardinal

point. Clockworks are capable of functioning 'dynamically',

because they are built of solids, which are kept in shape by

London-Beitler forces, strong enough to elude the disorderly

tendency of heat motion at ordinary temperature.

Now, I think, few words more are needed to disclose the

point of resemblance between a clockwork and an organism.

It is simply and solely that the latter also hinges upon a solidthe

aperiodic crystal forming the hereditary substance, largely

withdrawn from the disorder of heat motion. But please do not

accuse me of calling the chromosome fibres just the 'cogs of the

organic machine '-at least not without a reference to the profound

physical theories on which the simile is based.

For, indeed, it needs still less rhetoric to recall the fundamental

difference between the two and to justify the epithets

novel and unprecedented in the biological case.

The most striking features are: first, the curious distribution

of the cogs in a many-celled organism, for which I may refer

to the somewhat poetical description on p. 84; and secondly,

the fact that the single cog is not of coarse human make, but is

the finest masterpiece ever achieved along the lines of the

Lord's quantum mechanics.

EPILOGUE

ON DETERMINISM AND FREE WILL

As a reward for the serious trouble I have taken to expound

the purely scientific aspect of our problem sine ira et studio, I

beg leave to add my own, necessarily subjective, view of the

philosophical implications.

According to the evidence put forward in the preceding pages

the space-time events in the body of a living being which correspond

to the activity of its mind, to its self-conscious or any other

actions, are ( considering also their complex structure and the

accepted statistical explanation of physico-chemistry) if not

strictly deterministic at any rate statistico-deterministic. To the

physicist I wish to emphasize that in my opinion, and contrary

to the opinion upheld in some quarters, quantum indeterminacy

plays no biologically relevant role in them, except perhaps by

enhancing their purely accidental character in such events as

meiosis, natural and X-ray-induced mutation and so on-and

this is in any case obvious and well recognized.

For the sake of argument, let me regard this as a fact, as I

believe every unbiased biologist would, if there were not the

well-known, unpleasant feeling about 'declaring oneself to be

a pure mechanism'. For it is deemed to contradict Free Will

as warranted by direct introspection.

But immediate experiences in themselves, however various

and disparate they be, are logically incapable of contradicting

each other. So let us see whether we cannot draw the correct,

non-contradictory conclusion from the following two premises:

(i) Iv1y body functions as a pure mechanism according to the

Laws of Nature.

(ii) Yet I know, by incontrovertible direct experience, that I

On Determinisman d Pree Will 93

am directing its motions, of which I foresee the effects, that

may be fatefal andl all-important, in which case I feel and take

full responsibility for them.

The only possible inference from these two facts is, I think,

that 1-1 in the widest meaning of the word, that is to say,

every conscious mind that has ever said or felt ' I '-am the

person, if any, who controls the' motion of the atoms' according

to the Laws of Nature.

Within a cultural milieu (Kalturkreis)w here certain conceptions

(which once had or still have a wider meaning amongst

other peoples) have been limited and specialized, it is daring

to give to this conclusion the simple wording that it requires.

In Christian termitnology to s3:y : 'Hence I am God Almighty'

sounds both blasphemous and lunatic. But please disregard

these connotations for the moment and consider whether the

above inference is not the closest a biologist can get to proving

God and immortality at one stroke.

In itself, the insight is not new. The earliest records to my

knowledge date back some 2,500 years or more. From the early

great Upanishads the recognition ATHMAN = BRAHMAN (the

personal self equals the omnipresent, all-comprehending

eternal self) was iin Indian thought considered, far from being

blasphemous, to represent the quintessence of deepest insight

into the happenin~~so f the world. The striving of all the scholars

of Vedanta was, after having learnt to pronounce with their lips,

really to assimilat~: in their minds this grandest of all thoughts.

Again, the mys1ticso f many centuries, independently, yet in

perfect harmony with each other (somewhat like the particles

in an ideal gas) have described, each of them, the unique experience

of his or her life in terms that can be condensed in the

phrase: DEUS FACTUS SUM (I have become God).

To Western ideology the thought has remained a stranger, in

spite of Schopenhauer and others who stood for it and in spite

94 What is Life? Epilogue

of those true lovers who, as they look into each other's eyes,

become aware that their thought and their joy are numerically

one-not merely similar or identical; but they, as a rule, are

emotionally too busy to indulge in clear thinking, in which

respect they very much resemble the mystic.

Allow me a few further comments. Consciousness is never

experienced in the plural, only in the singular. Even in the

pathological cases of split consciousness or double personality

the two persons alternate, they are never manifest simultaneously.

In a dream we do perform several characters at the same

time, but not indiscriminately: we are one of them; in him we

act and speak directly, while we often eagerly await the answer

or response of another person, unaware of the fact that it is we

who control his movements and his speech just as much as our

own.

How does the idea of plurality (so emphatically opposed by

the Upanishad writers) arise at all? Consciousness finds itself

intimately connected with, and dependent on, the physical

state of a limited region of matter, the body. (Consider the

changes of mind during the development of the body, as

puberty, ageing, dotage, etc., or consider the effects of fever,

intoxication, narcosis, lesion of the brain and so on.) Now, there

is a great plurality of similar bodies. Hence the pluralization of

consciousnesses or minds seems a very suggestive hypothesis.

Probably all simple, ingenuous people, as well as the great

majority of Western philosphers, have accepted it.

It leads almost immediately to the invention of souls, as

many as there are bodies, and to the question whether they

are mortal as the body is or whether they are immortal and

capable of existing by themselves. The former alternative is

distasteful, while the latter frankly forgets, ignores or disowns

the facts upon which the plurality hypothesis rests. Much

sillier questions have been asked: Do animals also have souls?

On Determinisma nd Free Will 95

It has even been questioned whether women, or only men, have

souls.

Such consequences, even if only tentative, must make us

suspicious of the plurality hypothesis, which is common to all

official Western creeds. Aie we not inclining to much greater

nonsense, if in discarding their gross superstitions we retain

their naive idea of plurality of souls, but 'remedy' it by declaring

the souls to be perishable, to be annihilated with the

respective bodies ?

The only possible alternative is simply to keep to the immediate

experience that consciousness is a singular of which

the plural is unknown; that there is only one thing and that

what seems to be a plurality is merely a series of different

aspects of this one thing, produced by a deception (the Indian

MAJA); the same illusion is produced in a gallery of mirrors,

and in the same way Gaurisankar and Mt Everest turned out

to be the same peak seen from different valleys.

There are, of course, elaborate ghost-stories fixed in our

minds to hamper our acceptance of such simple recognition.

E.g. it has been said that there is a tree there outside my window

but I do not really see the tree. By some cunning device of

which only the initial, relatively simple steps are explored, the

real tree throws an image of itself into my consciousness, and

that is what I perceive. If you stand by my side and look at

the same tree, the latter manages to throw an image into your

soul as well. I see my tree and you see yours (remarkably like

mine), and what the tree in itself is we do not know. For this

extravagance Kant is responsible. In the order of ideas which

regards consciousness as a singulare tantum it is conveniently

replaced by the statement that there is obviously only one tree

and all the image business is a ghost-story.

Yet each of us has the indisputable impression that the sum

total of his own experience and memory forms a unit, quite

96 What is Life? Epilogue

distinct from that of any other person. He refers to it as 'I'.

What is this 'I'?

If you analyse it closely you will, I think, find that it is just

a little bit more than a collection of single data ( experiences and

memories), namely the canvas upon which they are collected.

And you will, on close introspection, find that what you

really mean by 'I' is that ground-stuff upon which they are

collected. You may come to a distant country, lose sight of

all your friends, may all but forget them; you acquire new

friends, you share life with them as intensely as you ever did

with your old ones. Less and less important will become the

fact that, while living your new life, you still recollect the old

one. 'The youth that was I', you may come to speak of him in

the third person, indeed the protagonist of the novel you are

reading is probably nearer to your heart, certainly more

intensely alive and better known to you. Yet there has been no

intermediate break, no death. And even if a skilled hypnotist

succeeded in blotting out entirely all your earlier reminiscences,

you would not find that he had killed you. In no case is there a

loss of personal existence to deplore.

Nor will there ever be.

NOTE TO THE EPILOGUE

The point of view taken here levels with what Aldous Huxley has

recently-and very appropriately-called Perennial Philosophy. His

beautiful book (London, Chatto and Windus, 1946) is singularly fit

to explain not only the state of affairs, but also why it is so difficult to

grasp and so liable to meet with opposition.

MIND AND MATTER

THE TARNER LECTURES

delivered at Trinity College, Cambridge,

in October z956

To

my famous and

belovedfr iend

HANS HOFF

in deep devotion

CHAPTER I

THE PHYSICAL BASIS OF

CONSCIOUSNESS

THE PROBLEM

The world is a construct of our sensations, perceptions,

memories. It is convenient to regard it as existing objectively

on its own. But it certainly does not become manifest by its

mere existence. Its becoming manifest is conditional on very

special goings-on in very special parts of this very world,

namely on certain events that happen in a brain. That is an

inordinately peculiar kind of implication, which prompts the

question: What particular properties distinguish these brain

processes and enable them to produce the manifestation?

Can we guess which material processes have this power,

which not? Or simpler: What kind of material process is

directly associated with consciousness?

A rationalist may be inclined to deal curtly with this question,

roughly as follows. From our own experience, and as

regards the higher animals from analogy, consciousness is

linked up with certain kinds of events in organized, living

matter, namely, with certain nervous functions. How far back

or 'down' in the animal kingdom there is still some sort of

consciousness, and what it may be like in its early stages, are

gratuitous speculations, questions that cannot be answered

and which ought to be left to idle dreamers. It is still more

gratuitous to indulge in thoughts about whether perhaps other

events as well, events in inorganic matter, let alone all material

events, are in some way or other associated with consciousness.

All this is pure fantasy, as irrefutable as it is unprovable, and

thus of no value for knowledge.

100 Mind and Matter

He who accepts this brushing aside of the question ought

to be told what an uncanny gap he thereby allows to remain

in his picture of the world. For the turning-up of nerve cells

and brains within certain strains -of organisms is a very special

event whose meaning and significance is quite well understood.

It is a special kind of mechanism by which the individual

responds to alternative situations by accordingly alternating

behaviour, a mechanism for adaptation to a changing surrounding.

It is the most elaborate and the most ingenious

among all such mechanisms, and wherever it turns up it

rapidly gains a dominating role. However, it is not sui generis.

Large groups of organisms, in particular the plants, achieve

very similar performances in an entirely different fashion.

Are we prepared to believe that this very special turn in the

development of the higher animals, a turn that might after all

have failed to appear, was a necessary condition for the world

to flash up to itself in the light of consciousness ? Would it

otherwise have remained a play before empty benches, not

existing for anybody, thus quite properly speaking not existing?

This would seem to me the bankruptcy of a world picture.

The urge to find a way out of this impasse ought not to be

damped by the fear of incurring the wise rationalists' mockery.

According to Spinoza every particular thing or being is a

modification of the infinite substance, i.e. of God. It expresses

itself by each of his attributes, in particular that of extension

and that of thought. The first is its bodily existence in space

and time, the second is-in the case of a living man or animalhis

mind. But to Spinoza any inanimate bodily thing is at

the same time also 'a thought of God', that is, it exists in the

second attribute as well. We encounter here the bold thought

of universal animation, though not for the first time, not even

in Western philosophy. Two thousand years earlier the

Ionian philosophers acquired from it the surname of hylozoists.

The Physical Basis of Consciousness IOI

After Spinoza the genius of Gustav Theodor Fechner did not shy

at attributing a soul to a plant, to the earth as a celestial body, to

the planetary system, etc. I do not fall in with these fantasies,

yet I should not like to have to pass judgment as to who has come

nearer to the deepest truth, Fechner or the bankrupts of

rationalism.

A TENTATIVE ANSWER

You see that all the attempts at extending the domain of consciousness,

asking oneself whether anything of the sort might

be reasonably associated with other than nervous processes,

needs must run into unproved and unprovable speculation.

But we tread on firmer ground when we start in the opposite

direction. Not every nervous process, nay by no means every

cerebral process, is accompanied by consciousness. Many of

them are not, even though physiologically and biologically

they are very much like the 'conscious' ones, both in frequently

consisting of afferent impulses followed by efferent ones, and

in their biological significance of regulating and timing reactions

partly inside the system, partly towards a changing

environment. In the first instance we meet here with the reflex

actions in the vertebral ganglia and in that part of the nervous

system which they control. But also ( and this we shall make

our special study) many re.fil.exivper ocesses exist that do pass

through the brain, yet do not fall into consciousness at all or

have very nearly ceased to do so. For in the latter case the

distinction is not sharp; intermediate degrees between fully

conscious and completely unconscious occur. By examining

various representatives of physiologically very similar processes,

all playing within our own body, it ought not to be too

difficult to find out by observation and reasoning the distinctive

characteristics we are looking for.

To my mind the key is to be found in the following well!

02 Mind and Matter

known facts. Any succession of events in which we take part

with sensations, perceptions and possibly with actions

gradually. drops out of the domain of consciousness when the

same string of events repeats itself in the same way very often.

But it is immediately shot up into the conscious region, if at

such a repetition either the occasion or the environmental

conditions met with on its pursuit differ from what they were on

all the previous incidences. Even so, at first anyhow, only those

modifications or ' differentials' intrude into the conscious

sphere that distinguish the new incidence from previous ones and

thereby usually call for 'new considerations'. Of all this each of

us can supply dozens of examples out of personal experience,

so that I may forgo enumerating any at the moment.

The gradual fading from consciousness is of outstanding

importance to the entire structure of our mental life, which is

wholly based on the process of acquiring practice by repetition,

a process which Richard Semon has generalized to the concept

of Mneme, about which we shall have more to say later. A single

experience that 1s never to repeat itself is biologically irrelevant.

Biological value lies only in learning the suitable reaction to a

situation that offers itself again and again, in many cases

periodically, and always requires the same response if the

organism is to hold its ground. Now from our own inner

experience we know the following. On the first few repetitions

a new element turns up in the mind, the 'already met with' or

'notal' as Richard Avenarius has called it. On frequent repetition

the whole string of events becomes more and more of a

routine, it becomes more and more uninteresting, the responses

become ever more reliable according as they fade from consciousness.

The boy recites his poem, the girl plays her piano

sonata 'well-nigh in their sleep'. We follow the habitual path

to our workshop, cross the road at the customary places, turn into

side-streets, etc., whilst our thoughts are occupied with entirely

The Physical Basis o/Consciousness 103

different things. But whenever the situation exhibits a relevant

differential-let us say the road is up at the place where we used

to cross it, so that we have to make a detour-this differential

and our response to it intrude into consciousnessf, rom which,

however, they soon fade below the threshold, if the differential

becomes a constantly repeated feature. Faced with changing

alternatives, bifurcations develop and may be fixed in the same

way. We branch off to the University Lecture Rooms or to the

Physics Laboratory at the right point without much thinking,

provided that both are frequently occurring destinations.

Now in this fashion differentials, variants of response,

bifurcations, etc., are piled up one upon the other in unsurveyable

abundance, but only the most recent ones remain in the

domain of consciousness, only those with regard to which the

living substance is still in the stage of learning or practising.

One might say, metaphorically,t hat consciousnessi s the tutor

who supervises the education of the living substance, but leaves

his pupil alone to deal with all those tasks for which he is already

sufficientlytr ained.B ut I wish to underlinet hree timesi n red ink

that I mean this only as a metaphor. The fact is only this, that new

situations and the new responses they prompt are kept in the light

of consciousness; old and well practised ones are no longer so.

Hundreds and hundreds of manipulations and performances

of everyday life had all to be learnt once, and that with great

attentiveness and painstaking care. Take for example a small

child's first attempts in walking. They are eminently in the

focus of consciousness; the first successes are hailed by the

performer with shouts of joy. When the adult laces his boots,

switches on the light, takes off his clothes in the evening, eats

with knife and fork . . . , these performances, that all had to be

toilsomely learnt, do not in the least disturb him in the thoughts

in which he may just be engaged.T his may occasionallyr esult

in comical miscarriages. There is the story of a famous mathe104

Mind and Matter

matician, whose wife is said to have found him lying in his bed,

the lights switched off, shortly after an invited evening party

had gathered in his house. What had happened? He had gone

to his bedroom to put on a fresh shirt-collar. But the mere

action of taking off the old collar had released in the man,

deeply entrenched in thought, the string of performances that

habitually followed in its wake.

Now this whole state of affairs, so well known from the

ontogeny of our mental life, seems to me to shed light on the

phylogeny of unconscious nervous processes, as in the heart

beat, the peristalsis of the bowels, etc. Faced with nearly constant

or regularly changing situations, they are very well and

reliably practised and have, therefore, long ago dropped from

the sphere of consciousness. Here too we find intermediate

grades, for example, breathing, that usually goes on inadvertently,

but may on account of differentials in the situation,

say in smoky air or in an attack of asthma, become modified and

conscious. Another instance is the bursting into tears for

sorrow, joy or bodily pain, an event which, though conscious,

can hardly be influenced by will. Also comical miscarriages of a

mnemically inherited nature occur, as the bristling of the hair

by terror, the ceasing of secretion of saliva on intense excitement,

responses which must have had some significance in the

past, but have lost it in the case of man.

I doubt whether everybody will readily agree with the next

step, which consists in extending these notions to other than

nervous processes. For the moment I shall only briefly hint at

it, though to me personally it is the most important one.. For

this generalization precisely sheds light on the problem from

which we started: What material events are associated with, or

accompanied by, consciousness, what not? The answer that I

suggest is as follows: What in the preceding we have said and

shown to be a property of nervous processes is a property of

The Physical Basis of Consciousness 105

organic processes :in general, namely, to be associated with

consciousness inasmuch as they are new. •

In the notion :and terminology of Richard Semon the

ontogeny not only of the brain but of the whole individual soma

is the 'well memorized' repetition of a string of events that have

taken place in much the same fashion a thousand times before.

Its first stages, as we know from our own experience, are

unconscious-first in the mother's womb; but even the ensuing

weeks and months of life are for the greatest part passed in

sleep. During this time the infant carries on an evolution of old

standing and habit, in which it meets with conditions that from

case to case vary V(:ry little. The ensuing organic development

begins to be accompanied by consciousness only inasmuch as

there are organs that gradually take up interaction with the

environment, adapt their functions to the changes in the

situation, are influenced, undergo practice, are in special ways

modified by the surroundings. We higher vertebrates possess

such an organ mainly in our nervous system. Therefore

consciousness is associated wiith those of its functions that

adapt themelves by what we call experience to a changing

environment. The 11ervouss ystem is the place where our species

is still engaged in phylogenetic transformation; metaphorically

speaking it is the 'vegetation top' (Vegetationsspitze)o f our

stem. I would summarize my general hypothesis thus: consciousness

is associated with the learning of the living substance;

its knowingh ow (Konne,n)is unconscious.

ETHICS

Even without this last generalization, which to me is very

important but may still seem rather dubious to others, the

theory of consciousness that I have adumbrated seems to pave

the way toward a scientific understanding of ethics.

/

106 Mind and Matter

At all epochs and with all peoples the background of every

ethical code (Tugendlehre)to be taken seriously has been, and

is, self-denial (Selbstuberwindung)T. he teaching of ethics

always assumes the form of a demand, a challenge, of a 'thou

shalt', that is in some way opposed to our primitive will.

Whence comes this peculiar contrast between the ' I will' and

the' thou shalt' ? Is it not absurd that I am supposed to suppress

my primitive appetites, disown my true self, be different from

what I really am? Indeed in our days, more perhaps than in

others, we hear this demand often enough mocked at. 'I am as

I am, give room to my individuality I Free development to the

desires that nature has planted in me! All the shalls that oppose

me in this are nonsense, priests' fraud. God is Nature, and

Nature may be credited with having formed me as she wants

me to be.' Such slogans are heard occasionally. It is not easy

to refute their plain and brutal obviousness. Kant's imperative·

is avowedly irrational.

But fortunately the scientific foundation of these slogans is

worm-eaten. Our insight into the 'becoming' ( das Werden) of

the organisms makes it easy to understand that our conscious

life-I will not say shall be, but that it actually is necessarily a

continued fight against our primitive ego. For our natural self,

our primitive will with its innate desires, is obviously the mental

correlate of the material bequest received from our ancestors.

Now as a species we are developing, and we march in the frontline

of generations; thus every day of a man's life represents a

small bit of the evolution of our species, which is still in full

swing. It is true that a single day of one's life, nay even any

individual life as a whole, is but a minute blow of the chisel at

the ever unfinished statue. But the whole enormous evolution

we have gone through in the past, it too has been brought about

by myriads of such minute chisel blows. The material for this

transformation, the presupposition for its taking place, are of

The Physical Basis ofConsciousness 107

course the inheritable spontaneous mutations. However, for

selection among them, the behaviour of the carrier of the

mutation, his habits of life, are of outstanding importance and

decisive influence. Otherwise the origin of species, the ostensibly

directed trends along which selection proceeds, could not

be understood even in the long spaces of time which are after

all limited and whose limits we know quite well.

And thus at every step, on every day of our life, as it were,

something of the shape that we possessed until then has to

change, to be overcome, to be deleted and replaced by something

new. The resistance of our primitive will is the psychical

correlate of the resistance of the existing shape to the transforming

chisel. For we ourselves are chisel and statue, conquerors

and conquered at the same time-it is a true continued

'self-conquering' (Selbstuberwindung).

But is it not absurd to suggest that this process of evolution

should directly and significantly fall into consciousness, considering

its inordinate slowness not only compared with the

short span of an individual life, but even with historical epochs ?

Does it not just run along unnoticed ?

No. In the light of our previous considerations this is not

so. They culminated in regarding consciousness as associated

with such physiological goings-on as are still being transformed

by mutual interaction with a changing environment. Moreover,

we concluded that only those modifications become conscious

which are still in the stage of being trained, until, in a much

later time, they become a hereditarily fixed, well-trained and

unconscious possession of the species. In brief: consciousness

is a phenomenon in the zone of evolution. This world lights up

to itself only where or only inasmuch as it develops, procreates

new forms. Places of stagnancy slip from consciousness; they

may only appear in their interplay with places of evolution.

If this is granted it follows that consciousness and discord

108 Mind and Matter

with one's own self are inseparably linked up, even that they

must, as it were, be proportional to each other. This sounds a

paradox, but the wisest of all times and peoples have testified

to confirm it. Men and women for whom this world was lit in

an unusually bright light of awareness, and who by life and

word have, more than others, formed and transformed that

work of art which we call humanity, testify by speech and

writing or even by their very lives that more than others have

they been torn by the pangs of inner discord. Let this be a

consolation to him who also suffers from it. Without it nothing

enduring has ever been begotten.

Please do not misunderstand me. I am a scientist, not a

teacher of morals. Do not take it that I wish to propose the idea

of our species developing towards a higher goal as an effective

motive to propagate the moral code. This it cannot be, since it

is an unselfish goal, a disinterested motive, and thus, to be

accepted, already presupposes virtuousness. I feel as unable as

anybody else to explain the 'shall' of Kant's imperative. The

ethical law in its simplest general form (be unselfish!) is plainly

a fact, it is there, it is agreed upon even by the vast majority of

those who do not very often keep it. I regard its puzzling

existence as an indication of our being in the beginning of a

biological transformation from an egoistic to an altruistic

general attitude, of man being about to become an animal social.

For a solitary animal egoism is a virtue that tends to preserve

and improve the species; in any kind of community it becomes

a destructive vice. An animal that embarks on forming states

without greatly 1-estricting egoism will perish. Phylogenetically

much older state-formers as the bees, ants and termites have

given up egoism completely. However, its next stage, national

egoism or briefly nationalism, is still in full swing with them.

A worker bee that goes astray to the wrong hive is murdered

without hesitation.

The Physical Basis o/Consciousness 109

Now in man something is, so it seems, on the way that is not

infrequent. Above the first modification clear traces of a second

one in similar direction are noticeable long before the first is

even nearly achieved. Though we are still pretty vigorous

egoists, many of us begin to see that nationalism too is a vice

that ought to be given up. Here perhaps something very strange

may make its appearance. The second step, the pacification of

the struggle of peoples, may be facilitated by the fact that the

first step is far from being achieved, so that egoistic motives still

have a vigorous appeal. Each one of us is threatened by the

terrific new weapons of aggression and is thus induced to long

for peace among the nations. If we were bees, ants or Lacedaemonian

warriors, to whom personal fear does not exist and

cowardice is the most shameful thing in the world, warring

would go on for e:ver. But luckily we are only men-and

cowards.

The considerations and conclusions of this chapter are, with

me, of very old standing; they date back more than thirty years.

I never lost sight of them, but I was seriously afraid that they

might have to be rejected on the ground that they appear to be

based on the 'inheritance of acquired characters', in other

words on Lamarckism. This we are not inclined to accept. Yet

even when rejecting the inheritance of acquired characters, in

other words accepting Darwin's Theory of Evolution, we find

the behaviour of the individuals of a species having a very

significant influence on the trend of evolution, and thus feigning

a sort of sham-Lamarckism. This is explained, and clinched

by the authority of Julian Huxley, in the following chapter,

which, however, was written with a slightly different problem

in view, and not just to lend support to the ideas put forward

above.

CHAPTER 2

THE FUTURE OF UNDERSTANDING 1

A BIOLOGICAL BLIND ALLEY?

We may, I believe, regard it as extremely improbable that our

understanding of the world represents any definite or final

stage, a maximum or optimum in any respect. By this I do not

mean merely that the continuation of our research in the various

sciences, our philosophical studies and religious endeavour are

likely to enhance and improve our present outlook. What we

are likely to gain in this way in the next, say, two and a half

millennia-estimating from what we have gained since

Protagoras, Democritus and Antisthenes-is insignificant compared

with what I am here alluding to. There is no reason

whatever for believing that our brain is the supremene plus ultra

of an organ of thought in which the world is reflected. It is

more likely than not that a species could acquire a similar contraption

whose corresponding imagery compares with ours as

ours with that of the dog, or his in turn with that of a snail.

If this be so, then-though it is not relevant in principle-it

interests us, as it were for personal reasons, whether anything

of the sort could be reached on our globe by our own offspring

or the offspring of some of us. The globe is all right. It is a fine

young leasehold, still to run under acceptable conditions of

living for about the time it took us (say 1,000 million years) to

develop from the earliest beginnings into what we are now.

But are we ourselves all right? If one accepts the present theory

of evolution-and we have no better-it might seem that we

1 The material in this chapter was first broadcast as a series of three talks in the

European Service of the B.B.C. in September 1950, and subsequently included

in What is Life .2 and other essays (Anchor Book A 88, Doubleday and Co.,

New York).

The Future of Understanding III

have been very nearly cut off from future development. Is there

still physical evolution to be expected in man, I mean to say

relevant changes in our physique that become gradually fixed

as inherited features, just as our present bodily self is fixed by

inheritance-genotypical changes, to use the technical term of

the biologist ? This question is difficult to answer. We may be

approaching the end of a blind alley, we may even have reached

it. This would not be an exceptional event and it would not

mean that our species would have to become extinct very soon.

From the geological records we know that some species or even

large groups seem to have reached the end of their evolutionary

possibilities a very long time ago, yet they have not died out, but

have remained unchanged, or without significant change, for

many millions of years. The tortoises, for instance, and the

crocodiles are in this sense very old groups, relics of a far remote

past; we are also told that the whole large group of insects are

more or less in the same boat-and they comprise a greater

number of separate species than all the rest of the animal

kingdom taken together. But they have changed very little in

millions of years, while the rest of the living surface of the earth

has during this time undergone change beyond recognition.

What barred further evolution in the insects was probably this

-that they had adopted the plan (you will not misunderstand

this figurative expression)-that they had adopted the plan of

wearing their skeleton outside instead of inside as we do. Such

an outside armour, while affording protection in addition to

mechanical stability, cannot grow as the bones of a mammal do

between birth and maturity. This circumstance is bound to

render gradual adaptive changes in the life-history of the

individual very difficult.

In the case of man several arguments seem to militate against

further evolution. The spontaneous inheritable changes-now

called mutations-from which, according to Darwin's theory,

II2 Mind and Matter

the 'profitable' ones are automatically selected, are as a rule

only small evolutionary steps, affording, if any, only a slight

advantage. That is why in Darwin's deductions an important

part is attributed to the usually enormous abundance of offspring,

of which only a very small fraction can possibly survive.

For only thus does a small amelioration in the chance of survival

seem to have a reasonable likelihood of being realized. This

whole mechanism appears to be blocked in civilized man-in

some respects even reversed. We are, generally speaking, not

willing to see our fellow-creatures suffer and perish, and so we

have gradually introduced legal and social institutions which

on the one hand protect life, condemn systematic infanticide,

try to help every sick or frail human being to survive, while on

the other hand they have to replace the natural elimination of

the less fit by keeping the offspring within the limits of the

available livelihood. This is achieved partly in a direct way, by

birth control, partly by preventing a considerable proportion

of females from mating. Occasionally-as this generation knows

all too well-the insanity of war and all the disasters and

blunders that follow in its wake contribute their share to the

balance. Millions of adults and children of both sexes are killed

by starvation, exposure, epidemics. While in the far remote

past warfare between small tribes or clans is supposed to have

had a positive selection value, it seems doubtful whether it ever

had in historical times, and doubtless war at present has none.

It means an indiscriminate killing, just as the advances in

medicine and surgery result in an indiscriminate saving oflives.

\Vhile justly and diametrically opposite in our esteem, both war

and medical art seem to be of no selection value whatever.

The Future of Understanding rr3

THE APPARENT GLOOM OF

DARWINISM

These considerations suggest that as a developing species we

have come to a standstill and have little prospect of further

biological advance. Even if this were so, it need not bother us.

\Ve might survive without any biological change for millions

of years, like the crocodiles and many insects. Still from a

certain philosophical point of view the idea is depressing, and

I should like to try and make out a case for the contrary. To do

so I must enter on a certain aspect of the theory of evolution

which I find supported in Professor Julian Huxley's well-known

book on Evolution,1 an aspect which according to him is not

always sufficiently appreciated by recent evolutionists.

Popular expositions of Darwin's theory are apt to lead you

to a gloomy and discouraging view on account of the apparent

passivity of the organism in the process of evolution. Mutations

occur spontaneously in the genom-the 'hereditary substance'.

We have reason to believe that they are mainly due to what the

physicist calls a thermodynamic fluctuation-in other words

to pure chance. The individual has not the slightest influence

on the hereditary treasure it receives from its parents, nor on

the one it leaves to its offspring. Mutations that occur are acted

on by 'natu:ral selection of the fittest'. This again seems to

mean pure chance, since it means that a favourable mutation

increases the prospect for the individual of survival and of

begetting offspring, to which it transmits the mutation in

question. Apart from this, its activity during its lifetime seems

to be biologically irrelevant. For nothing of it has any influence

on the offspring: acquired properties are not inherited. Any

skill or training attained is lost, it leaves no trace, it dies with

the individual, it ii; not transmitted. An intelligent being in this

1 Evolution: A Modern Synthesis (George Allen and Un win, 1942).

rr4 Mind and Matter

situation would find that nature, as it were, refuses his collaboration-

she does all herself, dooms the individual to inactivity,

indeed to nihilism.

As you know, Darwin's theory was not the first systematic

theory of evolution. It was preceded by the theory of Lamarck,

which rests entirely on the assumption that any new features an

individual has acquired by specific surroundings or behaviour

during its lifetime before procreation can be, and usually are,

passed on to its progeny, if not entirely, at least in traces. Thus

if an animal by living on rocky or sandy soil produced protecting

calluses on the soles of its feet, this callosity would gradually

become hereditary so that later generations would receive it as

a free gift without the hardship of acquiring it. In the same way

the strength or skill or even substantial adaptation produced in

any organ by its being continually used for certain ends would

not be lost, but passed on, at least partly, to the offspring. This

view not only affords a very simple understanding of the

amazingly elaborate and specific adaptation to environment

which is so characteristic of all living creatures. It is also

beautiful, elating, encouraging and invigorating. It is infinitely

more attractive than the gloomy aspect of passivity apparently

offered by Darwinism. An intelligent being which considers

itself a link in the long chain of evolution may, under Lamarck's

theory, be confident that its striving and efforts for improving

its abilities, both bodily and mental, are not lost in the

biological sense but form a small but integrating part of

the striving of the species towards higher and ever higher

perfection.

Unhappily Lamarckism is untenable. The fundamental

assumption on which it rests, namely, that acquired properties

can be inherited, is wrong. To the best of our knowledge they

cannot. The single steps of evolution are those spontaneous and

fortuitous mutations which have nothing to do with the

The Future of Understanding II5

behaviour of the individual during its lifetime. And so we

appear to be thrown back on the gloomy aspect of Darwinism

that I have depicted above.

BEHAVIOUR INFLUENCES SELECTION

I now wish to show you that this is not quite so. Without

changing anything in the basic assumptions of Darwinism we

can see that the behaviour of the individual, the way it makes

use of its innate faculties, plays a relevant part, nay, plays the

most relevant part in evolution. There is a very true kernel in

Lamarck's view, namely that there is an irrescindable causal

connection between the functioning, the actually being put to

profitable use of a character-an organ, any property or ability

or bodily feature-and its being developed in the course of

generations, and gradually improved for the purposes for which

it is profitably used. This connection, I say, between being

used and being improved was a very correct cognition of

Lamarck's, and it subsists in our present Darwinistic outlook,

but it is easily overlooked on viewing Darwinism superficially.

The course of events is almost the same as if Lamarckism were

right, only the 'mechanism' by which things happen is more

complicated than Lamarck thought. The point is not very easy

to explain or to grasp, and so it may be useful to summarize the

result in advance. To avoid vagueness, let us think of an organ,

though the feature in question might be any property, habit,

device, behaviour, or even any small addition to, or modification

of, such a feature. Lamarck thought that the organ (a) is used,

(b) is thus improved, and (c) the improvement is transmitted to

the offspring. This is wrong. We have to think that the organ

(a) undergoes chance variations, (b) the profitably used ones

are accumulated or at least accentuated by selection, (c) this

continues from generation to generation, the selected mutations

n6 Mind and Matter

constituting a lasting improvement. The most striking simulation

of Lamarckism occurs-according to Julian Huxleywhen

the initial variations that inaugurate the process are not

true mutations, not yet of the inheritable type. Yet, if profitable,

they may be accentuated by what he calls organic selection,

and, so to speak, pave the way for true mutations to be immediately

seized upon when they happen to turn up in the' desirable'

direction.

Let us now go into some details. The most important point

is to see that a new character, or modification of a character,

acquired by variation, by mutation or by mutation plus some

little selection, may easily arouse the organism in relation to its

environment to an activity that tends to increase the usefulness

of that character and hence the 'grip' of selection on it. By

possessing the new or changed character the individual may be

caused to change its environment-either by actually transforming

it, or by migration-or it may be caused to change its

behaviour towards its environment, all this in a fashion so as

strongly to reinforce the usefulness of the new character and

thus to speed up its further selective improvement in the same

direction.

This assertion may strike you as daring, since it seems to

require purpose on the side of the individual, and even a high

degree of intelligence. But I wish to make the point that my

statement, while it includes, of course, the intelligent, purposeful

behaviour of the higher animals, is by no means restricted to

them. Let us give a few simple examples:

Not all the individuals of a population have exactly the same

environment. Some of the flowers of a wild species happen to

grow in the shadow, some in sunny spots, some in the higher

ranges of a lofty mountain-slope, some in the lower parts or in

the valley. A mutation-say hairy foliage-which is beneficial

at higher altitudes, will be favoured by selection in the higher

The Future of Understanding n7

ranges but will be 'lost' in the.valley. The effect is the same as

if the hairy mutants had migrated towards an environment that

will favour further mutations that occur in the same direction.

Another example: their ability to fly enables birds to build

their nests high up in the trees where their young ones are less

accessible to some of their enemies. Primarily those who took

to it had a selectional advantage. The second step is that this

kind of abode was bound to select the proficient fliers among

the young ones. Thus a certain ability to fly produces a change

of environment, or behaviour towards the environment, which

favours an accumulation of the same ability.

The most remarkable feature among living beings is that

they are divided into species which are, many of them, so

incredibly specialized on quite particular, often tricky performances,

on which especially they rely for survival. A zoological

garden is almost a curiosity show, and would be much more so,

could it include au insight into the life-history of insects. Nonspecialization

is the exception. The rule is specialization in

peculiar studied tricks which 'no body would think of if nature

had not made them'. It is difficult to believe that they have all

resulted from Darwinian 'accumulation by chance'. Whether

one wants it or not, one is taken by the impression of forces or

tendencies away from' the plain and simple' in certain directions

towards the complicated. The 'plain and simple' seems to

represent an unstable state of affairs. A departure from it

provokes forces--so it seems-towards a further departure,

and in the same direction. That would be difficult to understand

if the development of a particular device, mechanism, organ,

useful behaviour, were produced by a long pearlstring of chance

events, independent of each other, such as one is used to thinking

of in terms of Darwin's original conception. Actually, I

believe, only the first small start 'in a certain direction' has this

structure. It produces itself circumstances which 'hammer the

II8 Mind and 111.atter

plastic material' -by selection-more and more systematically

in the direction of the advantage gained at the outset. In

metaphorical speech one might say: the species has found out

in which direction its chance in life lies and pursues this path.

FEIGNED LAMARCKISM

We must try to understand in a general way, and to formulate

in a non-animistic fashion, how a chance-mutation, which gives

the individual a certain advantage and favours its survival in a

given environment, should tend to do more than that, namely

to increase the opportunities for its being profitably made use

of, so as to concentrate on itself, as it were, the selective

influence of the environment.

To reveal this mechanism let the environment be schematically

described as an ensemble of favourable and unfavourable

circumstances. Among the first are food, drink, shelter, sunlight

and many others, among the latter are the dangers from

other living beings (enemies), poisons and the roughness of the

elements. For brevity we shall refer to the first kind as 'needs'

and to the second as 'foes'. Not every need can be obtained, not

every foe avoided. But a living species must have acquired a

behaviour that strikes a compromise in avoiding the deadliest

foes and satisfying the most urgent needs from the sources of

easiest access, so that it does survive. A favourable mutation

makes certain sources more easily accessible, or reduces the

danger from certain foes, or both. It thereby increases the

chance of survival of the individuals endowed with it, but in

addition it shifts the most favourable compromise, because it

changes the relative weights of those needs or foes on which it

bears. Individuals which-by chance or intelligence-change

their behaviour accordingly will be more favoured, and thus

selected. This change of behaviour is not transmitted to the

The Future of Understanding II9

next generation by the genom, not by direct inheritance, but

this does not mean that it is not transmitted. The simplest, most

primitive example is afforded by our species of flowers (with a

habitat along an extended mountain slope) that develops a

hairy mutant. The hairy mutants, favoured mainly in the top

ranges, disperse their seeds in such areas so that the next

generation of 'hairies ', taken as a whole, has 'climbed ur the

slope', as it were, 'to make better use of their favourable

mutation'.

In all this one must bear in mind that as a rule the whole

situation is extremely dynamic, the struggle is a very stiff one.

In a fairly prolific population that, at the time, survives without

appreciably increasing, the foes usually overpower the needsindividual

survival is an exception . .Nloreover, foes and needs

are frequently coupled, so that a pressing need can only be met

by braving a certain foe. (For instance, the antelope has to come

to the river for drink, but the lion knows the place just as well

as he.) The total pattern of foes and needs is intricately interwoven.

Thus a slight reduction of a certain danger by a given

mutation may make a considerable difference for those mutants

who brave that danger and thereby avoid others. This may

result in a noticeable selection not only of the genetic feature in

question but also with regard to the (intended or haphazard)

skill in using it. That kind of behaviour is transmitted to the

offspring by example, by learning, in a generalized sense of the

word. The shift of behaviour, in turn, enhances the selective

value of any further mutation in the same direction.

The effect of such a display may have great similarity with

the mechanism as pictured by Lamarck. Though neither an

acquired behaviour nor any physical changes that it entails are

directly transmitted to the offspring, yet behaviour has an

important say in the process. But the causal connection is not

what Lamarck thought it to be, rather just the other way round.

120 Mind and Matter

It is not that the behaviour changes the physique of the parents

and, by physical inheritance, that of the offspring. It is the

physical change in the parents that modifies-directly or indirectly,

by selection-their behaviour; and this change of

behaviour is, by example or teaching or even more primitively,

transmitted to the progeny, along with the physical change

carried by the genom. Nay, even if the physical change is not

yet an inheritable one, the transmission of the induced behaviour

'by teaching' can be a highly efficient evolutionary

factor, because it throws the door open to receive future

inheritable mutations ,vith a prepared readiness to make the

best use of them and thus to subject them to intense selection.

GENETIC FIXATION OF HABITS AND SKILLS

One mibht object that what we have here described may happen

occasionally, but cannot continue indefinitely to form the

essential mechanism of adaptive evolution. For the change of

behaviour itself is not transmitted by physical inheritance, by

the hereditary substance, the chromosomes. At first, therefore,

it is certainly not fixed genetically and it is difficult to see how

it should ever come to be incorporated in the hereditary

treasure. This is an important problem in itself. For we do

know that habits are inherited as, for instance, habits of nestbuilding

in the birds, the various habits of cleanliness we

observe in our dogs and cats, to mention a few obvious examples.

If this could not be understood along orthodox Darwinian

lines, Darwinism would have to be abandoned. The question

becomes of singular significance in its application to man, since

we wish to infer that the striving and labouring of a man during

his lifetime constitute an integrating contribution to the

development of the species, in the quite proper biological sense.

I believe the situation to be, briefly, as follows.

The Future of Understanding I2I

According to our assumptions the behaviour changes parallel

those of the physique, first as a consequence of a chance change

in the latter, but very soon directing the further selectional

mechanism into definite channels, because, according as

behaviour has availed itself of the first rudimentary benefits,

only further mutations in the same direction have any selective

value. But as (let me say) the new organ develops, behaviour

becomes more and more bound up with its mere possession.

Behaviour and physique merge into one. You simply cannot

possess clever hands without using them for obtaining your

aims, they would be in your way (as they often are to an

amateur on the stage, because he has only fictitious aims). You

cannot have efficient wings without attempting to fly. You cannot

have a modulated organ of speech without trying to imitate

the noises you hear around you. To distinguish between the

possession of an organ and the urge to use it and to increase its

skill by practice, to regard them as two different characteristics

of the organism in question, would be an artificial distinction,

made possible by an abstract language but having no counterpart

in nature. \Ve must, of course, not think that 'behaviour'

after all gradually intrudes into the chromosome structure ( or

what not) and acquires 'loci' there. It is the new organs themselves

(and they do become genetically fixed) that carry along

with them the habit and the way of using them. Selection would

be powerless in 'producing' a new organ if selection were not

aided all along by the organism's making appropriate use of it.

And this is very essential. For thus, the two things go quite

parallel and are ultimately, or indeed at every stage, fixed

genetically as one thing: a used organ-as if Lamarck were

right.

It is illuminating to compare this natural process with the

making of an instrument by man. At first sight there appears to

be a marked contrast. If we manufacture a delicate mechanism,

5 SWl

122 Mind and Matter

we should in most cases spoil it if we were impatient and tried

to use it again and again long before it is finished. Nature, one

is inclined to say, proceeds differently. She cannot produce a

new organism and its organs otherwise than whilst they are

continually used, probed, examined with regard to their

efficiency. But actually this parallel is wrong. The making of a

single instrument by man corresponds to ontogenesis, that is,

to the growing up of a single individual from the seed to

maturity. Here too interference is not welcome. The young

ones must be protected, they must not be put to work before

they have acquired the full strength and skill of their species.

The true parallel of the evolutionary development of organisms

could be illustrated, for example, by a historical exhibition of

bicycles, showing how this machine gradually changed from

year to year, from decade to decade; or, in the same way, of

railway-engines, motor-cars, aeroplanes, typewriters, etc. Here,

just as in the natural process, it is obviously essential that the

machine in question should be continually used and thus

improved; not literally improved by use, but by the experience

gained and the alterations suggested. The bicycle, by the way,

illustrates the case, mentioned before, of an old organism,

which has reached the attainable perfection and has therefore

pretty well ceased to undergo further changes. Still it is not

about to become extinct!

DANGERS TO INTELLECTUAL EVOLUTION

Let us now return to the beginning of this chapter. We started

from the question: is further biological development in man

likely ? Our discussion has, I believe, brought to the fore two

relevant points.

The first is the biological importance of behaviour. By conforming

to innate faculties as well as to the environment and by

The Future of Understanding 123

adapting itself to changes in either of these factors, behaviour,

though not itself inherited, may yet speed up the process of

evolution by orders of magnitude. While in plants and in the

lower ranges of the animal kingdom adequate behaviour is

brought aoout by the slow process of selection, in other words

by trial and error, man's high intelligence enables him to enact

it by choice. This incalculable advantage may easily outweigh

his handicap of slow and comparatively scarce propagai..ion,

which is further reduced by the biologically dangerous regard

not to let our offspring exceed the volume for which livelihood

can be secured.

The second point, concerning the question whether biological

development is still to be expected in man, is intimately

connected with the first. In a way we get the full answer, namely,

this will depend on us and our doing. We must not wait for

things to come, believing that they are decided by irrescindable

destiny. If we want it, we must do something about it. If not,

not. Just as the political and social development and the

sequence of historical events in general are not thrust upon us

by the spinning of the Fates, but largely depend on our own

doing, so our biological future, being nothing else but history

on a large scale, must not be taken to be an unalterable destiny

that is decided in advance by any Law of Nature. To us at any

rate, who are the acting subjects in the play, it is not, even

though to a superior being, watching us as we watch the birds

and the ants, it might appear to be. The reason why man tends

to regard history, in the narrower and in the wider sense, as a

predestined happening, controlled by rules and laws that he

cannot change, is very obvious. It is because every single

individual feels that he by himself has very little say in the

matter, unless he can put his opinions over to many others and

persuade them to regulate their behaviour accordingly.

As regards the concrete behaviour necessary to secure our

s-a

124 Mind and Matter

biological future, I will only mention one general point that I

consider of primary importance. We are, I believe, at the

moment in grave danger of missing the 'path to perfection'.

From all that has been said, selection is an indispensable

requisite for biological development. If it is entirely ruled out,

development stops, nay, it may be reversed. To put it in the

words of Julian Huxley: ' ... the preponderance of degenerative

(loss) mutation will result in degeneration of an organ when it

becomes useless and selection is accordingly no longer acting

on it to keep it up to the mark.'

Now I believe that the increasing mechanization and

'stupidization' of most manufacturing processes involve the

serious danger of a general degeneration of our organ of intelligence.

The more the chances in life of the clever and of the

unresponsive worker are equalled out by the repression of

handicraft and the spreading of tedious and boring work on the

assembly line, the more will a good brain, clever hands and a

sharp eye become superfluous. Indeed the unintelligent man,

who naturally finds it easier to submit to the boring toil, will be

favoured; he is likely to find it easier to thrive, to settle down

and to beget offspring. The result may easily amount even to

a negative selection as regards talents and gifts.

The hardship of modern industrial life has led to certain

institutions calculated to mitigate it, such as protection of the

workers against exploitation and unemployment, and many

other welfare and security measures. They are duly regarded

as beneficial and they have become indispensable. Still we

cannot shut our eyes to the fact that, by alleviating the responsibility

of the individual to look after himself and by levelling the

chances of every man, they also tend to rule out the competition

of talents and thus to put an efficient brake on biological evolution.

I realize that this particular point is highly controversial.

One may make a strong case that the care for our present

The Future of Understanding 125

welfare must override the worry about our evolutionary future.

But fortunately, so I believe, they go together according to my

main argument. Next to want, boredom has become the worst

scourge in our lives. Instead of letting the ingenious machinery

we have invented produce an increasing amount of superfluous

luxury, we must plan to develop it so that it takes off human

beings all the unintelligent, mechanical, 'machine-like'

handling. The machine must take over the toil for which man

is too good, not m~m the work for which the machine is too

expensive, as comes to pass quite often. This will not tend to

make production cheaper, but those who are engaged in it

happier. There is small hope of putting this through as long

as the competition between big firms and concerns all over the

world prevails. But this kind of competition is as uninteresting

as it is biologically worthless. Our aim should be to reinstate

in its place the interesting and intelligent competition of single

human beings.

CHAPTER 3

THE PRINCIPLE OF OBJECTIVATION

Nine years ago I put forward two general principles that form

the basis of the scientific method, the principle of the understandability

of nature, and the principle of objectivation. Since

then I have touched on this matter now and again, last time in

my little bookNature and the Greeks.1 I wish to deal here in

detail with the second one, the objectivation. Before I say what

I mean by that, let me remove a possible misunderstanding

which might arise, as I came to realize from several reviews of

that book, though I thought I had prevented it from the outset.

It is simply this: some people seemed to think that my intention

was to lay down the fundamental principles which ought to be

at the basis of scientific method or at least which justly and

rightly are at the basis of science and ought to be kept at all

cost. Far from this, I only maintained and maintain that they

are-and, by the way, as an inheritance from the ancient

Greeks, from whom all our Western science and scientific

thought has originated.

The misunderstanding is not very astonishing. If you hear a

scientist pronounce basic principles of science, stressing two

of them as particularly fundamental and of old standing, it is

natural to think that he is at least strongly in favour of them

and wishes to impose them. But on the other hand, you see,

science never imposes anything, science states. Science aims at

nothing but making true and adequate statements about its

object. The scientist only imposes two things, namely truth

and sincerity, imposes them upon himself and upon other

scientists. In the present case the object is science itself, as it

1 Cambridge University Press, 1954,

The Principleo fObjectivation

has developed and has become and at present is, not as it ought

to be or ought to develop in future .

. Now let us turn to these two principles themselves. As

regards the first, 'that nature can be understood', I will say here

only a few words. The most astonishing thing about it is that

it had to be invented, that it was at all necessary to invent it. It

stems from the Milesian School, the physiologoiS. ince then it

has remained untouched, though perhaps not always uncontaminated.

The present line in physics is possibly a quite

serious contamination. The uncertainty principle, the alleged

lack of strict causal connection in nature, may represent a step

away from it, a partial abandonment. It would be interesting to

discuss this, but I set my heart here on discussing the other

principle, that which I called objectivation.

By this I mean the thing that is also frequently called the

'hypothesis of the real world' around us. I maintain that it

amounts to a certain simplification which we adopt in order to

master the infinitely intricate problem of nature. Without being

aware of it and without being rigorously systematic about it,

we exclude the Subject of Cognizance from the domain of

nature that we endeavour to understand. We step with our own

person back into the part of an onlooker who does not belong

to the world, which by this very procedure becomes an objective

world. This device is veiled by the following two circumstances.

First, my own body (to which my mental activity is so very

directly and intimately linked) forms part of the object ( the real

world around me) that I construct out of my sensations, perceptions

and memories. Secondly, the bodies of other people

form part of this objective world. Now I have very good reasons

for believing that these other bodies are also linked up with, or

are, as it were, the seats of spheres of consciousness. I can have

no reasonable doubt about the existence or some kind of

actualness of these foreign spheres of consciousness, yet I have

128 Mind and Matter

absolutely no direct subjective access to any of them. Hence I

am inclined to take them as something objective, as forming part

of the real world around me. Moreover, since there is no distinction

between myself and others, but on the contrary full

symmetry for all intents and purposes, I conclude that I myself

also form part of this real material world around me. I so to

speak put my own sentient self (which had constructed this

world as a mental product) back into it-with the pandemonium

of disastrous logical consequences that flow from the

aforesaid chain of faulty conclusions. \Ve shall point them out

one by one; for the moment let me just mention the two most

blatant antinomies due to our unawareness of the fact that a

moderately satisfying picture of the world has only been

reached at the high price of taking ourselves out of the picture,

stepping back into the role of a non-concerned observer.

The first of these antinomies is the astonishment at finding

our world picture 'colourless, cold, mute'. Colour and sound,

hot and cold are our immediate sensations; small wonder that

they are lacking in a world model from which we have removed

our own mental person.

The second is our fruitless quest for the place where mind

acts on matter or vice-versa, so well known from Sir Charles

Sherrington's honest search, magnificently expounded in Afan

on his Nature. The material world has only been constructed at

the price of taking the self, that is, mind, out of it, removing it;

mind is not part of it; obviously, therefore, it can neither act on

it nor be acted on by any of its parts. (This was stated in a very

brief and clear sentence by Spinoza, seep. r3r.)

I wish to go into more detail about some of the points I have

made First let me quote a passage from a paper of C. G. Jung

which has gratified me because it stresses the same point in

quite a different context, albeit in a strongly vituperative

The Principleo fObjectivation 129

fashion. While I continue to regard the removal of the Subject

of Cognizance from the objective world picture as the high

price paid for a fairly satisfactory picture, for the time being,

Jung goes further and blames us for paying this ransom from,an

inextricably difficult situation. He says:

All science (Wissenschaft)h owever is a function of the soul, in

which all knowledge is rooted. The soul is the greatest of all cosmic

miracles, it is the conditios ineq uan ono f the world as an object. It is

exceedingly astonishing that the Western world (apart from very rare

exceptions) seems to have so little appreciation of this being so. The

flood of external objects of cognizance has made the subject of all

cognizance withdraw to the background, often to apparent nonexistence.

1

Of course Jung is quite right. It is also clear that he, being

engaged in the science of psychology, is much more sensitive

to the initial gambit in question, much more so than a physicist

or a physiologist. Yet I would say that a rapid withdrawal from

the position held for over 2,000 years is dangerous. We may lose

everything without gaining more than some freedom in a special

-though very important-domain. But here the problem is

set. The relatively new science of psychology imperatively

demands living-space, it makes it unavoidable to reconsider the

initial gambit. This is a hard task, we shall not settle it here and

now, we must be c:ontent at having pointed it out.

While here we found the psychologist Jung complaining

about the exclusion of the mirid, the neglect of the soul, as he

terms it, in our world picture, I should now like to adduce in

contrast, or perhaps rather as a supplement, some quotations

of eminent representatives of the older and humbler sciences

of physics and physiology, just stating the fact that 'the world

of science' has become so horribly objective as to leave no room

for the mind and its immediate sensations.

1 EranosJ ahrbuch( 1946), p. 398.

130 Mind and Matter

Some readers may remember A. S. Eddington's 'two

writing desks'; one is the familiar old piece of furniture at which

he is seated, resting his arms on it, the other is the scientific

physical body which not only lacks all and every sensual qualities

but in addition is riddled with holes; by far the greatest

part of it is empty space, just nothingness, interspersed with

innumerable tiny specks of something, the electrons and the

nuclei whirling around, but always separated by distances at

least 100,000 times their own size. After having contrasted the

two in his wonderfully plastic style he summarizes thus:

In the world of physics we watch a shadowgraph performance of

familiar life. The shadow of my elbow rests on the shadow table as the

shadow ink flows over the shadow paper ... The frank realization that

physical science is concerned with a world of shadows is one of the

most significant of recent advances.1

Please note that the very recent advance does not lie in the

world of physics itself having acquired this shadowy character;

it had it ever since Democritus of Abdera and even before, but

we were not aware of it; we thought we were dealing with the

world itself; expressions like model or picture for the conceptual

constructs of science came up in the second half of the

nineteenth century, and not earlier, as far as I know.

Not much later Sir Charles Sherrington published his

momentous Man on hisNature.2 The book is pervaded by the

honest search for objective evidence of the interaction between

matter and mind. I stress the epithet 'honest', because it does

need a very serious and sincere endeavour to look for something

which one is deeply convinced in advance cannot be found,

because (in the teeth of popular belief) it does not exist. A

brief summary of the result of this search is found on p. 357:

1 The Nature of the Physical World (Cambridge University Press, 1928), Introduction.

3 Cambridge University Press, 1940.

The Principleo f Objectivation 131

Mind, for anything perception can compass, goes therefore in our

spatial world more ghostly than a ghost. Invisible, intangible, it is a

thing not even of outline; it is not a 'thing'. It remains without

sensual confirmation and remains without it forever.

In my own words I would express this by saying: Mind has

erected the objective outside world of the natural philosopher

out of its own stuff. Mind could not cope with this gigantic

task otherwise than by the simplifying device of excluding

itself-withdrawing from its conceptual creation. Hence the

latter does not contain its creator.

I cannot convey the grandeur of Sherrington's immortal

book by quoting sentences; one has to read it oneself. Still, I

will mention a few of the more particularly characteristic.

Physical science ... faces us with the impasse that mind per se cannot

play the piano-mind per se cannot move a finger of a hand (p. 222 ).

Then the impasse meets us. The blank of the 'how' of mind's

leverage on matter. The inconsequence staggers us. Is it a misunderstanding?

(p. 232).

Hold these conclusions drawn by an experimental physiologist

of the twentieth century against the simple statement of

the greatest philosopher of the seventeenth century: B. Spinoza

(Ethics, Pt 111, Prop. 2):

Nee corpus mentem ad cogitandum nee mens corpus ad motum

neque ad quietem nee ad aliquid (si quid est) aliud determinare

potest.

[Neither can the body determine the mind to think, nor the mind

determine the body to motion or rest or anything else (if such there

be).]

The impasse is an impasse. Are we thus not the doers of our

deeds ? Yet we feel responsible for them, we are punished or

praised for them, as the case may be. It is a horrible antinomy.

I maintain that it cannot be solved on the level of present-day

science which is still entirely engulfed in the 'exclusion

132 Mind and Matter

principle '-without knowing it-hence the antinomy. To

realize this is valuable, but it does not solve the problem. You

cannot remove the 'exclusion principle' by act of parliament

as it were. Scientific attitude would have to be rebuilt, science

must be made anew. Care is needed.

So we are faced with the following remarkable situation.

While the stuff from which our world picture is built is yielded

exclusively from the sense organs as organs of the mind, so that

every man's world picture is and always remains a construct of

his mind and cannot be proved to have any other existence, yet

the conscious mind itself remains a stranger within that construct,

it has no living space in it, you can spot it nowhere in

space. We do not usually realize this fact, because we have

entirely taken to thinking of the personality of a human being,

or for that matter also that of an animal, as located in the

interior of its body. To learn that it cannot really be found there

is so amazing that it meets with doubt and hesitation, we are

very loath to admit it. We have got used to localizing the conscious

personality inside a person's head-I should say an inch

or two behind the midpoint of the eyes. From there it gives us,

as the case may be, understanding or loving or tender-or

suspicious or angry looks. I wonder has it ever been noted that

the eye is the only sense organ whose purely receptive character

we fail to recognize in naive thought. Reversing the actual state

of affairs, we are much more inclined to think of' rays of vision',

issuing from the eye, than of the 'rays of light' that hit the eyes

from outside. You quite frequently find such a 'ray of vision'

represented in a drawing in a comic paper, or even in some

older schematic sketch intended to illustrate an optic instrument

or law, a dotted line emerging from the eye and pointing

to the object, the direction being indicated by an arrowhead at

the far end.-Dear reader or, better still, dear lady reader, recall

the bright, joyful eyes with which your child beams upon you

The Principle ofObjectivation 133

when you bring him a new toy, and then let the physicist tell

you that in reality nothing emerges from these eyes; in reality

their only objectively detectable function is, continually to be

hit by and to rec1eiveli ght quanta. In reality! A strange reality!

Something seems to be missing in it.

It is very difficult for us to take stock of the fact that the

localization of the personality, of the conscious mind, inside

the body is only symbolic, just an aid for practical use. Let us,

with all the knowledge we have about it, follow such a 'tender

look' inside the body. We do hit there on a supremely interesting

bustle or, if you like, machinery. We find millions of cells

of very specialized build in an arrangement that is unsurveyably

intricate but quite obviously serves a very far-reaching and

highly consummate mutual communication and collaboration;

a ceaseless hammering of regular electrochemical pulses which,

however, chang:e rapidly in their configuration, being conducted

from rnerve cell to nerve cell, tens of thousands of

contacts being opened and blocked within every split second,

chemical transformations being induced and maybe other

changes as yet undiscovered. All this we meet and, as the science

of physiology advances, we may trust that we shall come to

know more and more about it. But now let us assume that in a

particular case you eventually observe several efferent bundles

of pulsating currents, which issue from the brain and through

long cellular protrusions (motor nerve fibres), are conducted

to certain muscles of the arm, which, as a consequence, tends

a hesitating, trembling hand to you to bid you farewell-for a

long, heart-rending separation; at the same time you may find

that some other pulsating bundles produce a certain glandular

secretion so as to veil the poor sad eye with a crape of tears. But

nowhere along this way from the eye through the central organ

to the arm muscles and the tear glands-nowhere, you may be

sure, however far physiology advances, will you ever meet the

134 Mind and Matter

personality, will you ever meet the dire pain, the bewildered

worry within this soul, though their reality is to you so certain

as though you suffered them yourself.-as in actual fact you do!

The picture that physiological analysis vouchsafes to us of any

other human being, be it our most intimate friend, strikingly

recalls to me Edgar Allan Poe's masterly story, which I am sure

many a reader remembers well; I mean The Masque of the Red

Death. A princeling and his retinue have withdrawn to an

isolated castle to escape the pestilence of the red death that

rages in the land. After a week or so of retirement they arrange

a great dancing feast in fancy dress and mask. One of the masks,

tall, entirely veiled, clad all in red and obviously intended to

represent the pestilence allegorically, makes everybody shudder,

both for the wantonness of the choice and for the suspicion

that it might be an intruder. At last a bold young man approaches

the red mask and with a sudden jolt tears off veil and head-gear.

It is found empty.

Now our skulls are not empty. But what we find there, in

spite of the keen interest it arouses, is truly nothing when held

against the life and the emotions of the soul.

To become aware of this may in the first moment upset one.

To me it seems, on deeper thought, rather a consolation. If you

have to face the body of a deceased friend whom you sorely

miss, is it not soothing to realize that this body was never really

the seat of his personality but only symbolically 'for practical

reference' ?

As an appendix to these considerations, those strongly

interested in the physical sciences might wish to hear me pronounce

on a line of ideas, concerning subject and object, that

has been given great prominence by the prevailing school of

thought in quantum physics, the protagonists being Niels

Bohr, Werner Heisenberg, Max Born and others. Let me first

The Principle o/Objectivation 135

give you a very brief description of their ideas. It runs as

follows:1

We cannot make any factual statement about a given natural

object ( or physical system) without 'getting in touch' with it.

This 'touch' is a real physical interaction. Even if it consists

only in our 'looking at the object' the latter must be hit by

light-rays and reflect them into the eye, or into some instrument

of observation. This means that the object is affected by our

observation. You cannot obtain any knowledge about an object

while leaving it strictly isolated. The theory goes on to assert

that this disturbance is neither irrelevant nor completely

surveyable. Thus after any number of painstaking observations

the object is left in a state of which some features (the last

observed) are known, but others (those interfered with by the

last observation) are not known, or not accurately known. This

state of affairs is offered as an explanation why no complete,

gapless description of any physical object is ever possible.

If this has to be granted-and possibly it has to be grantedthen

it flies in the face of the principle of understandability of

nature. This in itself is no opprobrium. I told you at the outset

that my two principles are not meant to be binding on science,

that they only express what we had actually kept to in physical

science for many, many centuries and what cannot easily be

changed. Personally I do not feel sure that our present knowledge

as yet vindicates the change. I consider it possible that our

models can be modified in such a fashion that they do not

exhibit at any moment properties that cannot in principle be

observed simultaneously-models poorer in simultaneous

properties but richer in adaptability to changes in the environment.

However, this is an internal question of physics, not to

be decided here and now. But from the theory as explained

before, from the unavoidable and unsurveyable interference of

1 See my Science and Humanism (Cambridge University Press, 1951), p. 49.

136 Mind and Matter

the measuring devices with the object under observation, lofty

consequences of an epistemological nature have been drawn and

brought to the fore, concerning the relation between subject

and object. It is maintained that recent discoveries in physics

have pushed forward to the mysterious boundary between the

subject and the object. This boundary, so we are told, is not a

sharp boundary at all. We are given to understand that we never

observe an object without its being modified or tinged by our

own activity in observing it. We are given to understand that

under the impact of our refined methods of observation and of

thinking about the results of our experiments that mysterious

boundary between the subject and the object has broken down.

In order to criticize these contentions let me at first accept

the time-hallowed distinction or discrimination between object

and subject, as many thinkers both in olden times have accepted

it and in recent times still accept it. Among the philosophers

who accepted it-from Democritus of Abdera down to the

'Old Man of Konigsberg'-there were few, if any, who did

not emphasize that all our sensations, perceptions and observations

have a strong, personal, subjective tinge and do not

convey the nature of the 'thing-in-itself', to use Kant's term.

While some of these thinkers might have in mind only a more

or less strong or slight distortion, Kant landed us with a complete

resignation: never to know anything at all about his

'thing-in-itself'. Thus the idea of subjectivity in all appearance

is very old and familiar. What is new in the present setting is

this: that not only would the impressions we get· from our

environment largely depend on the nature and the contingent

state of our sensorium, but inversely the very environment that

we wish to take in is modified by us, notably by the devices we

set up in order to observe it.

Maybe this is so-to some extent it certainly is. May be that

from the newly discovered laws of quantum physics this

The Principle of Objectivation 137

modification cannot be reduced below certain well-ascertained

limits. Still I would not like to call this a direct influence of the

subject on the object. For the subject, if anything, is the thing

that senses and thinks. Sensations and thoughts do not belong

to the 'world of energy', they cannot produce any change in

this world of energy as we know from Spinoza and Sir Charles

Sherrington.

All this was said from the point of view that we accept the

time-hallowed discrimination between subject and object.

Though we have to accept it in everyday life 'for practical

reference', we ought, so I believe, to abandon it in philosophical

thought. It:s rigid logical consequence has been revealed by

Kant: the sublime, but empty, idea of the 'thing-in-itself'

about which we forever know nothing.

It is the same elements that go to compose my mind and the

world. This situation is the same for every mind and its world,

in spite of the unfathomable abundance of 'cross-references'

between them. The world is given to me only once, not one

existing and one perceived. Subject and object are only one.

The barrier between them cannot be said to have broken down

as a result of rece:nt experience in the physical sciences, for this

barrier does not exist.

CHAPTER 4

THE ARITHMETICAL PARADOX:

THE ONENESS OF MIND

The reason why our sentient, percipient and thinking ego is

met nowhere within our scientific world picture can easily be

indicated in seven words: because it is itself that world picture.

It is identical with the whole and therefore cannot be contained

in it as a part of it. But, of course, here we knock against the

arithmetical paradox; there appears to be a great multitude of

these conscious egos, the world however is only one. This

comes from the fashion in which the world-concept produces

itself. The several domains of' private' consciousnesses partly

overlap. The region common to all where they all overlap is

the construct of the 'real world around us'. With all that an

uncomfortable feeling remains, prompting such questions as:

Is my world really the same as yours ? Is there one real world

to be distinguished from its pictures introjected by way of perception

into every one of us ? And if so, are these pictures like

unto the real world or is the latter, the world 'in itself', perhaps

very different from the one we perceive ?

Such questions are ingenious, but in my opinion very apt

to confuse the issue. They have no adequate answers. They all

are, or lead to, antinomies springing from the one source, which

I called the arithmetical paradox; the many conscious egos

from whose mental experiences the one world is concocted. The

solution of this paradox of numbers would do away with all the

questions of the aforesaid kind and reveal them, I dare say, as

sham questions.

There are two ways out of the number paradox, both appearing

rather lunatic from the point of view of present scientific

Oneness of Mind 139

thought (based on ancient Greek thought and thus thoroughly

'\1/ estern '). One way out is the multiplication of the world in

Leibniz's fearful doctrine of monads: every monad to be a

world by itself, no communication between them; the monad

'has no windows', it is' incommunicado'. That none the less they

all agree with each other is called 'pre-established harmony'.

I think there are few to whom this suggestion appeals, nay

who would consider it as a mitigation at all of the numerical

antinomy.

There is obviously only one alternative, namely the unification

of minds or consciousnesses. Their multiplicity is only

apparent, in truth there is only one mind. This is the doctrine

of the Upanishads. And not only of the Upanishads. The

mystically experienced union with God regularly entails this

attitude unless it is opposed by strong existing prejudices; and

this means that it is less easily accepted in the \1/ est than in the

East. Let me quote as an example outside the Upanishads an

Islamic Persian mystic of the thirteenth century, Aziz Nasafi.

I am taking it from a paper by Fritz Meyer1 and translating

from his German translation:

On the death of any living creature the spirit returns to the spiritual

world, the body to the bodily world. In this however only the bodies

are subject to change. The spiritual world is one single spirit who

stands like unto a light behind the bodily world and who, when any

single creature comes into being, shines through it as through a

window. According to the kind and size of the window less or more

light enters the world. The light itself however remains unchanged.

Ten yeftrS ago Aldous Huxley published a precious volume

which he called The Perennial Philosophy2 and which is an

anthology from the mystics of the most various periods and the

most various peoples. Open it where you will and you find many

beautiful utterances of a similar kind. You are struck by the

1 EranosJ ahrbuch,1 946. 2 Chatto and Windus, 1946.

Mind and Matter

miraculous agreement between humans of different race,

different religion, knowing nothing about each other's existence,

separated by centuries and millennia, and by the greatest

distances that there are on our globe.

Still, it must be said that to Western thought this doctrine