Philosophy and Philosophers - an Introduction to Western Philosophy - Chapter 2
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CHAPTER TWO
Greek philosophy:
Plato, Aristotle
The period of Greek philosophy that followed the Presocratics begins
around 400 BC; the most important figures are Socrates (470–399 BC),
Plato (427–347 BC), and Aristotle (384–322 BC). It is possible to discern
a shift in interest in Greek philosophy away from explanations of the
natural world to moral concerns, in the sense of discovering the best
way for men to live. The difficulties of determining what were the
objective or real features of the world, as opposed to those only
apparent features which depended on a point of view (and hence were
subjective), began to undermine the early explanations of natural
science. If we are uncertain about what features of the world are real
and what are only apparent, then it is unsurprising that such doubt
will extend to the objectivity of moral standards. The threat was of
moral anarchy.
To understand later Greek philosophy it is necessary to remember
some unsolved problems derived from the Presocratics. In one sense
Heraclitus stands at one extreme, Parmenides at the other. For
Heraclitus everything is in flux; there is no being, only becoming or
processes—although this becoming is subject to a cosmic logos or law
of change. Heraclitus holds a compositional theory of identity
whereby something remains the same thing only if the stuff out of
which it is made remains exactly the same stuff. The world as it
appears to the senses is argued by the Parmenideans to be an illusion:
it is a world that appears to involve change and plurality, but these
are impossible. The world for the Parmenideans is a plenum (full, or
containing no void), and change, movement, plurality and diversity
are impossible because they involve an X becoming a not-X (nonbeing,
or a nothing); but even not-X is something, therefore not-X is
self-contradictory, since it asserts of X both that “It is” and “It is not”.
Thus the appearance of change and plurality presented to us by the
senses is impossible, since it involves a contradiction; it is an illusion.
One answer derives from Democritus and the other atomists; the
21
attempt is made to reconcile the explanation of the empirical world
with the Parmenidean paradoxes; and the answer is to posit atoms
with Parmenidean oneness of being in a void, which lies beyond the
world as it appears. In just the way that Parmenidean arguments
demand, these atoms do not, in themselves, change or have parts, but
the appearance of change and diversity is explained by the coming
together and dissolution of aggregates of atoms combined with the
effect of these changes on us.
There are, however, problems with atomism. First, there is the
difficulty that the atomic world is by definition beyond appearances;
its existence cannot be empirically verified, it can only be posited, and
cannot be known to exist. Second, the properties that the atoms are
supposed to have are said to be objective or real because they are
properties which are independent of observers. On inspection the
suggested properties, such as size, shape, motion, seem to be equally
dependent as properties such as colour and heat on one’s point of
view. Thus X can be large to you, but small to me; X can be fast
moving to you, but slow moving to me; but it would be contradictory
to suppose that X has both properties, and since we have no reason for
choosing one appearance over the other, X cannot really have either of
these properties. No property can be real if its being-what-it-is is
dependent on the point of view or state of the observer in this way.
Third, mere aggregates of atoms, which might be said to make up
some thing (this horse), seem to give no account of the commonsense
or pre-theoretical notion of separate or independent individual kinds:
an independent “this so-and-so”. “This so-and-so” is an independent
or separable individual, uniquely distinguished from any other thing,
and can undergo certain changes while retaining its individuality or
identity as a “so-and-so”. The “so-and-so” of an individual “this” is
spelt out in its essential nature or “whatness”; the essence is those
features which are necessary and sufficient for it to exist as a
determinate kind of “so-and-so”. This reflects the difference between
an individual horse and a mere indeterminate lump of bronze. Without
real or substantial separate individuals there is the suggestion that
when we say something has become an X (“this so-and-so”), it is
purely conventional or relative, and dependent on how our language
happens to chop up the world; in reality no new substance has come
into being at all, there has just been a rearrangement of the only true
substances: the atoms.
These considerations lead to scepticism about our knowledge of
the empirical world. One answer, proposed by the Sophist
Protagoras (c.483–c.414 BC) is to embrace conventionalism or
relativism, and say that reality is not something independent of the
way human beings have come to divide things up through their
thought and language; there is no reality which is the way things are,
independently of the way we talk about it; what we take to be
22 Greek philosophy
relatively stable factors in the world are derived from facts about
how we talk about the world. The danger here to universal ethical
standards is obvious. If what in all cases we count as X and as
ceasing to be an X is merely a matter of conventional fact or relative
to a point of view then it could be thought to be a mere convention,
or relative only to a point of view, whether X is morally good or
right, bad or wrong. There is no longer any matter of objective fact; it
is just a function of the way we happen to talk, it is a relative truth
because our criteria for X, reflected in the meaning of the word for X,
could change. In the case both of empirical and of moral assertions,
we could adopt different conventions; and there would be no
grounds to choose between one or the other derived from pointing to
objective independent constraints in the world or outside our
conventions, for there are none. What seems good, from a certain
point of view, is good, and we cannot say objectively that one view is
more legitimate than another.
Plato
Plato was born into an aristocratic Athenian family. He is, along with
Aristotle, perhaps the most important figure in the history of Western
philosophy. As a man he is difficult to know, although a strong
personality plainly emerges from the many dialogues he wrote.
Although he thought of entering politics, he became finally
disillusioned with it following the execution of Socrates. Plato’s own
philosophical views take Socrates’ views as their starting-point; and
our knowledge of Socrates derives almost entirely from Plato’s
dialogues, in which Socrates is often the main character. Around 380
BC Plato founded the Academy for the propagation of knowledge and
education for the future rulers of Greek city-states. The Academy
would have been unlike a modern university, and more akin to a
college where there would be ritual communal activities, such as
taking meals together. Among the intellectuals of Athens were the
Sophists, or “experts”, who, unlike Socrates, charged for their teaching
services, giving instruction on rhetoric and efficacious behaviour in
public office. Socrates, like Plato, considered Sophist claims to
knowledge ill-founded, and set out to expose this fact; generally
Socrates regarded them as ignorant men who, worst of all, did not
even know they were ignorant. The curriculum of the Academy
included philosophy, mathematics, astronomy, and some natural
science. Later in life, Plato became reluctantly involved in a disastrous
visit to Sicily aimed at educating Dionysius II. Plato perhaps felt the
need to try to put his political philosophy into action. He returned to
Athens, and sheltered from the political storms around him. He died at
the age of eighty years old.
Plato 23
It is against the Presocratic background that the views of Socrates
and Plato emerge, starting with a concern for ethical matters; but the
same overall approach is applied to knowledge generally. Questions
are asked, for example, about what is good or what the good is; for
surely knowledge must be knowledge of what is. We can apply this
by taking the example of justice. Socrates does not simply state an
answer to the question; rather he admits his ignorance and asks his
interlocutors for hypotheses, which start with experience and the
inductive gathering of particular cases as a first step; he then goes on
to test the hypotheses through arguments demonstrating their
consequences, and shows that the answers merely give an example of
the thing he is after, and an example, moreover, that cannot be
justice-in-itself, but is merely justice from certain points of view that
cannot universally be called justice. What he is after is justice-initself
(the Just); justice without qualification or unconditionally. For
it is in virtue of a fixed justice-in-itself that all things, or all cases,
which we correctly call justice are justice. All those things we call
just must share some common and peculiar characteristic in virtue of
which we are correct to call them all just. To act justly, we need to
know what justice truly is. If we talk of X without knowing what X
is, we literally do not know what we are talking about. What
Socrates is seeking is a true or real definition; that is, not merely an
account of how we, in fact, use a word, nor a stipulated use, but a
definition that tells us of the true nature of the object or quality to
which the word applies; that is, its essence. This is similar to asking
for an objective account of what is justice, independent of any points
of view.
To have knowledge of something, X, involves understanding what
we truly mean by the term “X”; and understanding the true meaning
of “X” involves saying what X is—what the essential fixed nature of
X is—what it is for X to be the kind of thing it is. Socrates is
concerned not chiefly with the meaning of the word “X”, but with
the object X, and the real nature of X as determining the true
meaning of “X”.
Plato holds a realist theory of meaning and knowledge. The
meaning of terms and that which we come to know is a process of
discovering an existing objective reality “out there”, not a process of
creation which is relative to the apparatus—for example, language, or
the senses—we use for the inquiry. This notion of objectivity and
invariance of standards—of being able to say what X is—applies to
ethics and aesthetics, as well as science and mathematics; without
fixed reference points for the meanings of classificatory terms, all
significant talk about the world would be impossible; the world
would be a stream of unique ineffable particulars. The meanings of
words are, or can be, determined by the nature of reality—in existing
objective references—not the other way around. And if knowledge is
24 Greek philosophy
possible, it must be knowledge of objects which are real; and this
requires that knowledge be knowledge of what is; that is, objects that
are not in states of becoming, but are eternal, immutable beings. To
make our meanings match the world as it really is, is to seek true or
real definitions, and requires objects, which the definitions are
definitions of. The meaning of the word “justice” is not, in Plato’s
view, a mere conception in the mind, but is fixed mindindependently.
In agreeing with Heraclitus that the sensible world is in flux, Plato
realizes that the objects of such definitions are not going to be found
among imperfect and mutable sensible objects, but exist in a
supersensible realm of immutable objects “seen” by the intellect
beyond sense-experience. In the world we never find justice-in-itself,
but only conditional justice. One can always find conditions in which,
derived from a changing world or a different point of view, a just
action ceases to be a just action. Plato thinks there has to be something
that is invariable and common which corresponds to the meaning of
universal terms such as “justice” or “bed”, that exists over and above
the variety of particular instances that terms—such as “justice” or
“bed”—cover, and that justifies the classification or grouping of
various different things as of the same sort or class. What we mean by
“horse” in general, if it is meaningful at all, is something other than
any particular horse, each of which differs; each horse is a horse
because of its sharing in a nature common to all horses.
It is from the search for definitions of universal, immutable, ethical
standards that Plato’s theory of Forms emerges as the basis for all
knowledge (epist¯em¯e) in its full sense. Plato turns Socrates’ search for
definitions, aimed at understanding the nature of what we are talking
about, into an ontological claim whereby the real meaning of
classificatory terms requires a reference in a transcendent object or
Form (eidos). It is not just knowledge of ethical truths that requires the
Forms, but all claims to knowledge. Indeed, it applies to knowledge
itself, for if we cannot suppose there is some fixed meaning for the
term “knowledge”, referring to some fixed object, knowledge-in-itself,
then surely intellectual chaos must ensue. Plato assumed that for a
word to have any fixed objective meaning, this must be in virtue of a
fixed and objective entity to which the word refers. This assumption
can be questioned.
It is essential for the understanding of the theory of Forms to see
why epistemology and metaphysics are so closely connected in Plato’s
philosophy: the nature of knowledge should be matched by an
appropriate ontology. Knowledge is always knowledge of something, and
Plato requires these objects of knowledge to bear in their mode of
existing (the way they are as objects) the same characteristics as the
knowledge we have of those objects. For Plato, two main conditions
have to be met for the highest sort of knowledge.
Plato 25
(a) Universality or objectivity
Knowledge of something is not relative to a point of view;
knowledge should be something that would be true from any
point of view.
(b) Unchangingness, eternality or immutability
This requires that knowledge is unchanging over time; that if
something is knowledge, then it is knowledge once and for all;
it cannot cease to be knowledge. Knowledge in its highest
sense is infallible: it is absolutely certain. If one really knows
something, there cannot be conditions under which what one
knows is wrong, and ceases to be knowledge. So one knows
only what must be true—necessary truths—and cannot be false,
and when there is a method of demonstrating conclusively that
the known truths are necessary truths.
There are two factors that make the world of sensible objects
unsuitable for knowledge.
(a’) That things and properties in the sensible world are not fully real,
since they are not unconditionally what they appear, as how they
appear depends on a point of view. Sensible things can take on
contrary properties for this reason as well if one’s point of view
changes; the properties sensible things appear to have is therefore
determined partly subjectively.
(b’) That things in the sensible world are constantly changing. In this
way sensible things can take on contrary properties over time; the
sensible world is one of becoming.
Anything that can take on contrary properties cannot be fully real, since
it never unconditionally just is, and we cannot be said to be knowing
things as they are in themselves. Plato gives strict conditions for
knowledge: certainty, universality and immutability. He further needs to
show, if knowledge is possible, how we can satisfy those conditions; the
Forms of the theory of Forms provide objects which satisfy the
conditions for knowledge. Knowledge is knowledge of something; that
is, it requires an existing object; there must be objects of knowledge that
match the characteristics of knowledge proper (knowledge in its full
sense) itself if such knowledge is possible at all. These objects are the
Forms. The Forms are not objects in the sensible world; sensible objects
both are mutable and have properties that vary with one’s point of view,
and so are not fully objective; nor are the Forms posited entities that
underlie appearances in the way that atoms do. Forms subsist beyond
the flux of experience and space and time in a transcendent,
supersensible realm that is ultimately perceived purely by the intellect.
The Forms are pure objective essences, and as the objects of knowledge
they match the characteristics required of knowledge itself. As opposed
to the “thatness” or existence of things (that X is), the Forms define the
26 Greek philosophy
“whatness” or essence of things (what X is); the Forms give necessary
and sufficient conditions for things to be the kind of things they are. The
Forms have the following important characteristics.
(a’’) Universality or objectivity
There is no point of view from which the Form of F could be
sometimes F and sometimes not-F; if something can be both F
and not-F depending on a different point of view or different
circumstances, then we cannot have found F-in-itself: the Form of
F. The Forms are also what is universally or objectively true from
any point of view. Apprehending what things-are-in-themselves
is to grasp their Form. As well as being objects of knowledge in
themselves, the Forms are the extent to which anything can be
said to be universally or objectively true of sensible objects apart
from their various appearances.
(b’’) Unchangingness, eternality or immutability
Since the Form of F is immutable and indeed eternally what it is,
there is no time at which the Form of F can become not-F, it is
eternally F. Forms are fully real in that they are not characterized
by any becoming; they are being. They are what a sensible object
which copies or participates in a Form really is apart from its
changing states. The Forms are separate in some sense from the
world of sensible objects and their nature grasped by the senseindependent
intellect; their separateness seems to consist of real
existence or ontological independence apart from both sensible
things and minds.
Taking (a’’) and (b’’) together gives the conditions for the mode of
being of fully real existence, and this matches (a) and (b), the
conditions for knowledge proper.
Plato seems to hold that the realm of Forms is separate from the
realm of sensible objects, but exactly in what this separateness consists
is not clear. The sensible world is ontologically secondary; although
later in life Plato became more interested in natural science. It is worth
noting that since the Forms are not in space or time, it is senseless to
ask where the Forms are. It is the ontological separateness of the Forms
from particulars which is criticized by Aristotle.
It may not be immediately obvious why we cannot be said to have
knowledge of particular truths. Surely I can know that “there is a table
in my room”? However, it is worth noting that, regardless of its
certainty, we would hardly regard this as a piece of scientific
knowledge; it is not a universal explanatory law. Plato does not deny
that something beyond ignorance is possible in these cases: we can
have belief (doxa) which is true. But the highest form of knowledge,
knowledge in its full sense, is of universals or objective essences.
Knowledge proper is not of this or that table, but of tables-inthemselves:
knowledge of what is involved in something being a table:
Plato 27
tableness. Knowledge proper transcends the bounds even of all
possible experience, and involves an intellectual “seeing” that reveals
things as they are in themselves. If something is known in the highest
sense to be true, it cannot become false. If X is known, then necessarily
it is true that X. Plato goes further in holding—although it does not
follow from the assertion that knowledge entails truth—that if X is
known, then X is a necessary truth. Plato holds that what is known
must be true in the sense that what is known is only necessary truths;
knowledge is of things that could not be otherwise. If what is known
ceased to be true, it would cease to be knowledge. Take the example
“This water is hot”. The problem here for knowledge is that (a) “This
water is hot” can be true for one person, but false for another, and (b)
the water is something that is in a state of becoming (becoming cold
perhaps), so “This water is hot” is true, but will become false. That
which has no fixity cannot have true descriptions applied to it, for
what is true becomes instantly false.
The model for the ideal of knowledge is to be found not among the
mutable and relative truths concerning sensible objects, but among the
eternal and universal truths concerning the objects of mathematics and
geometry which are known by the intellect. The truths of arithmetic
and geometry concern not this or that object (say, a particular triangle),
or this or that set of objects (say, two pairs of objects), but rather
triangularity and 2+2=4. Knowing the truth 2+2=4 does not concern
any particular two objects, which might through change become one
or three objects, or which only look like two objects when viewed in a
certain way, or any sensible objects at all. Knowing the truth 2+2=4
concerns twoness, and its relation to other essences, such as equality,
addition, and fourness. This is not a truth that varies over time; indeed
it is eternal or timeless, and stands outside time; and, as such, this
known truth requires an eternal object of which the known truth is
true; that object is a Form or combination of Forms. The objects of the
sensible world are not suitable objects for such necessary, objective,
immutable truths. Take the example of equality: if we have two sticks
of equal length, and also observe that they are six feet long, we may be
tempted to say that being equal (equality) consists in being six feet
long; but there are circumstances in which being six feet long would be
both equal (F) and unequal (not-F); so we do not yet know equality-initself
because we have identified something—being six feet long—that
can be both equal and not-equal, whereas to know what equality-initself
is is to know it irrespective of changes over time, point of view, or
conditions. Equality as such must also be what all cases of equality
have in common irrespective of their particular differences.
The world of Forms is “perceived” by reason or the intellect, not the
senses; the Forms are objects of intellectual vision or looking.
Geometrical truths concern not this or that circle or triangle, nor
even generalizations about all empirical circles and triangles which are
28 Greek philosophy
also approximate and imperfect, but circularity and triangularity as
such known by the intellect alone—in short, they deal with essences—
with the Xness of objects under the common name “X”. It must be
noted that mathematical truths are one step down from knowledge of
the Forms themselves because mathematics still involves unquestioned
assumptions; but since mathematical truths known by the intellect
alone are superior in certainty and immutability to the deliverances of
the senses, they can be used as a stepping stone toward knowledge of
the Forms.
At a lower level than mathematics, we can further understand the
Platonic ideal of knowledge, and the requirement that it be objective,
through analogy with scientific laws of nature: Newton’s first law of
motion, “Every body continues in its state of rest, or of uniform motion
in a right line, unless it is compelled to change that state by forces
impressed upon it”, is not a law applicable only to particular bodies, or
bodies considered from a certain point of view; it at least applies to all
bodies at all times and in all places. Moreover, it may be said to apply
to bodies-as-such; that is to say, it is a truth which can be known about
the essence of bodies; to be concerned with the essence of bodies is to
be concerned with what all and only bodies have in common, that
which is necessary and sufficient for them to be bodies, which is
correctly called “body”.
It may be concluded that if knowledge of the Forms is the only true
knowledge, then there can be only ignorance of the objects of the
sensible world, and therefore that the sensible world is neglected by
Plato. But this is not the case. That the world perceived by the senses is
not fully real because it is subject to becoming (it never just “is”), and it
cannot be the object of universal, immutable, unconditional truths,
does not mean that it does not exist. The existence of immutable Forms
divides the world into various fixed kinds of things as they are in
themselves, and is the formal and final cause of the sensible objects in
the world (the world of becoming) having whatever limited degree of
being of which they are capable. “Cause” should be understood here in
a more general sense than that to which we are accustomed: causation
is an answer to a “Why?” by a “Because…”. The Forms are “formal
causes” in giving definite character to things which we bring under
common names (“man”); the Forms are “final causes” as the perfection
towards which that kind of thing aims as an end. As formal causes, the
Forms are a precondition for our saying of anything that it is
something of a specific kind; they define and make definite things as
objects of a certain type; they are thereby causes by giving definite
character and a limited degree of type-identity to the flux of the
sensible world.
Although Plato never answers the point, one assumes there must
be some limit to the number of classificatory divisions; if every
positive common name has a Form, then the danger is of an
Plato 29
unlimited and unknowable world of Forms. Relative terms such as
“large” are also problematic. Although the Forms do not give us
eternal, immutable particular sensible objects—for only universal
kinds or types are eternal and immutable—they give to sensible
objects a stability somewhere in between the being and non-being of
Parmenides, avoiding thereby the universal becoming of Heraclitus;
and of these sensible objects of relative stability we are able to have
true beliefs, if not knowledge. Plato points out that “is” does not
always mean “exists”. The exhaustive choice is not being X
(existence) and non-being X (non-existence or nothing); for we can
say that X can be an X while losing some properties and gaining
others. To say that a person X was hairy and is now bald is to say
there has been a change in X not from existence to non-existence, but
from being hairy to X being not hairy (bald). At the same time, Plato
attacks Protagoras’ relativism, which claims that universal objective
knowledge is not possible at all, and that we are merely left with
particular knowledge claims about immediate experience, which are
perhaps infallible (cannot be mistaken) in themselves, but which are
true only from a certain point of view at a certain time, with no claim
to universality or generality at all.
Plato’s answer to both Heraclitus and Parmenides is the Forms.
Plato agrees with Heraclitus that the world of sensible objects is
ultimately in flux, and he agrees with Parmenides that the intellect
alone knows the true nature of reality. Knowledge proper is of
immutable and eternal truths and must concern the nature of
immutable, eternal objects that really exist; but the sensible world
reveals only mutable, non-eternal objects; therefore, if knowledge is
possible, it must concern a realm of immutable, eternal objects that
really exist, beyond sense-experience, that are intuited or seen by the
intellect alone; those objects are the Forms.
Plato’s epistemology and metaphysics mirror each other: the Forms
which have only being are fully knowable; of utter non-being there can
only be ignorance; but in between these is the sensible world of
becoming of which there can be true belief which lies between full
knowability and complete ignorance. This gives the following picture.
Being (Forms) – knowledge
Becoming (sensible world) – true belief
Non-being (nothing) – ignorance
The way to approach true knowledge is by the method of dialectic:
giving, improving, and eventually destroying, hypotheses—
assumptions used for justification in the sense of reasoned grounds for
what we claim to know. Claims to knowledge are thereby based on
fewer and fewer, and different, assumptions. For it to be said that I
know X, it has to be the case not only that I have beliefs, even if they are
true, concerning X, but also that I can give an account of why it is true
30 Greek philosophy
that X, or what X is; a proper account or justification marks the
beginning of the distinction between belief and knowledge. Giving an
account of X is saying what it is that makes it X. The account that I give
may be based on assumptions which are not themselves beyond
question. If I try to account for X being true by deducing X from certain
premises, then it can be asked what justification I have for these
premises. I can answer this challenge by deducing the initial premises
themselves from more general premises. The method of hypothesis is a
process of questioning and testing deduced consequences of hypotheses.
The intellect or thought transcends, in mathematics, hypotheses about
the imperfect, approximate, objects of experience. We successively
ascend from hypothesis to hypothesis, until we eventually reach the
Forms, and ultimately the “First Principle” or highest Form the “Good”
or “Being” or the “One”, which is said to transcend even being, and
which is self-authenticating (unhypothesized) and destroys the need for
hypotheses.
Another related description of the dialectic found in the later work
of Plato is the method of division and collection: this is the process of
collection and division into genera and species, and it suggests a
hierarchy of Forms; the Forms are complex wholes which are divided
through genus and difference by species. The logic of the dialectic is
matched by an ontological process; the logical collection of species
under genus is like the blending into one another (in the manner of
colours) of different Forms. The aim of division in the dialectic is to
give real definitions of terms referring to indivisible “atomic Forms”
(infima species) such as “man”, “horse”, “tree”, that have no sub-species
and designate species or universals, not particulars or individuals. The
“atomic Forms” cannot combine at all: so the expression “man horses”
makes no sense at all. The hierarchy of Forms is describes a hierarchy
of reality or degrees of being proportional to permanence and
generality. Below the “atomic Forms” there are only individuals (for
example, individual men), not further species. Alternatively we can, by
collecting species, ascend in the hierarchy to ever more pervasively
general categories of being, to Forms of ever richer content and greater
degrees of being. It has also been suggested that Plato envisioned some
kind of mystical road to the highest Forms, as well as the rational
dialectic.
Plato’s view on epistemology and metaphysics can be summarized,
although not entirely in his terminology, in the following way. Reality
should determine language to give objective concepts which are not
our creation, but rather fixed, and imposed upon us. The highest sort
of knowledge is of objective necessary truths, which are discovered by
the intellectual inspection of the ways that non-conventional objective
universal concepts—discovered and not arbitrarily created—are
connected or not connected to each other. The necessary connections
concerning the highest sort of knowledge are found by intellectually
Plato 31
seeing the inclusion or non-inclusion of the true meanings of common
words—concepts—in each other. These concepts are objective in
describing the real eternal immutable nature of the Forms, which are
real eternal immutable objects. Some Forms are the essential features of
the objects to which common names refer, and determine and tell us
what each thing is in itself. The essential nature of a thing includes
only those features which are necessary and jointly sufficient for it to
be the kind of thing it is. The essential features are revealed in a true or
real definition of what it is for a thing to be of a determinate kind.
It is important to see that for Plato the concern is not with the
necessary connection of propositions, or merely with the meaning of
words, but with the nature of the objects the words stand for: real
immutable eternal objects—the Forms with the required characteristic
of being—understood by the sense-independent intellect through their
descriptive concepts revealed in definitions or formulae. These
ontological connections are revealed by linking the true meaning of
terms which name Forms, given by a true description of essences in
real definitions (providing a correct account or logos), which give
concepts of eternal existing objective Forms. The connection of these
concepts which name Forms is seen by the intellect in the inclusion or
non-inclusion of the meaning of one concept in another. This produces,
in the case of inclusion, a logically necessary truth concerning the
connection of the objects referred to. Such necessary connections,
which depend only on the inspection of correct meanings, produce
truths logically independent of experience. We can know necessary
truths by showing conceptual connections; and such necessary truths
are necessary because the terms in these truths have as their reference
eternal immutable objects—Forms—which are not, and cannot be,
objects of sense-experience, but are objects of the intellect. The dialectic
method is deductive, ensuring that knowledge is infallible (nonrevisable)
and certain; a truth known by the correct use of the method
cannot be shaken by new evidence. The dialectical method for
justifying truths cannot be valid by degree. It provides a way of
making the justification element in our knowledge a conclusive logical
proof: it is a valid argument deduced from necessary truths. In this
way the necessary truths which are known are conclusively shown to
be necessary, and hence to have the absolute certainty and
immutability required of knowledge proper.
The Platonic dialectic of collection and division approximates to the
modern notion of analyticity, and the discovery of analytic truths; but
Plato thinks that these are objective truths (they are true of the Forms)
and independent of the factual conventions of linguistic usage.
The inclusion and non-inclusion of meanings can be illustrated as
follows: “man” is included in the concept “animal”; and under the
concept “animal” falls the array of different animals; so “man is an
animal” is a necessary truth; whereas plainly “man” does not, and
32 Greek philosophy
indeed cannot, include the concept “fox”. Man and trousers are
connected, if at all, only contingently because the concept “man” (real
meaning or definition of “man”) does not include “trousers”; so “man
wears trousers” is not an eternal truth, and is not an object of the
highest knowledge (epist¯em¯e), but a matter of belief (doxa), perhaps true
belief, about a contingent fact in the sensible world.
No necessary truths picking out necessary connections can be
discovered in the sensible world; yet this is required if knowledge of
the sensible world is possible—in the highest sense of being absolutely
certain or infallible and eternal. Otherwise there are only correct
beliefs concerning contingent truths in the sensible world. If what is
known is a necessary truth, and can be shown to be a necessary truth,
then it is absolutely certainly known, since it is impossible that it
could be false. In any case, knowledge of the sensible world is
dependent on the availability of the absolute objective fixity of the
concepts we bring to the world, and this is guaranteed only by the
absolute objective fixity of concepts’ references in a real, supersensible
realm of Forms “perceived” by the intellect. Whether, and how, such
Forms, articulated in concepts, can be connected with the sensible
world is a difficult question. But even to say of anything that it “is X”
(“is yellow”) is to use the concept of being (being X) that goes beyond
the particular yellow percept, which may change. In the same way
being able meaningfully to say “that is a man” presupposes the
conceptual fixity of “man”. Plato thinks that meaningful talk about the
world must involve both that there must be absolute conceptual fixity
of meaning and also that such meaning is derived from a special
object: a Form.
There is an ascent to the Forms, and through the hierarchy of Forms,
until what we claim to know is a truth, where the justification is
deduced, by way of the relation of real definitions, from a startingpoint
which is self-authenticating, completely certain, and involves no
assumptions. We aim to ascend to this “First Principle”, from which
we see the whole of reality as a connected rational system based on the
absolute objectivity of the Forms. To the extent that anything like
knowledge of the sensible world is possible—and Plato’s interest in
natural science increased in later life—it involves a downward
dialectical process in the hierarchy of Forms: in this, one initially
proposes the most general class to which the thing to be defined (the
definiendum) belongs, until through division by similarity (by genus)
and difference (by species) we have specified the narrowest class the
thing defined belongs to; then we shall have knowledge in the fullest
sense of what the definiendum is: this gives the necessary and sufficient
conditions for a thing being the kind of thing it is. For example, the
definition of “triangle” combines the genus of “triangle” as “polygon”
with the species of polygon “having three sides” into “polygon having
three sides”. This fixes what a triangle is.
Plato 33
The taxonomy of the unchanging hierarchy of Forms is the true
object of knowledge. Through the Forms is revealed, in the terminal
definitions by genus and difference, the essence of things sharing a
positive common name. We also come to know the rules of
combination or blending of those Forms, since not all Forms can blend
together. An assertion suggesting the blending of incompatible
Forms—“motion is rest”—is a contradiction.
False judgements are not about nothing, but concern elements which
exist—say, the particular Theaetetus and the Form flying—but which, in
combination, are judged to assert falsely “Theaetetus flies”. Indeed,
every meaningful statement involves at least one universal or Form.
Through studying the interrelation of the Forms we come to know the
true unchanging or eternal structure of reality. The highest Form—the
“Good” or “Being”—is the genus of all that is real; a real whole
covering—common to—all and only that which is real. That is, the
highest Form is the essence of reality as such. The Forms exist in a world
that transcends both the physical and mental, while they are somehow
related to particulars. The Form of the “Good” or “Being” is the aim and
aspiration of all things, the ultimate ground of the world’s intelligible
reality through defining the nature of being or reality itself or as such.
Our ability to have knowledge of the Forms, transcending the
sensible world, is explained by Plato’s theory of recollection. One way
of interpreting this theory is to see it as Plato’s attempt to account for
the possibility of a priori knowledge; that is, truths known by the
intellect alone independently of sense-experience. At some time before
we were born, our immortal soul was disembodied and was thereby
not confused and distracted by sensible particulars. Our soul is part of
the eternal realm, and so able through pure reason to grasp the nature
of the Forms themselves. Indeed, the possibility of knowledge of
essences—the Forms—is taken as proof of our immortality. Sensible
objects remind us of the perfect Forms we have forgotten, of which
sensible objects are imperfect copies, and which have being only in so
far as they partake of the immutable divisions of reality or being of the
Forms. The extraction of universals by comparing sensible objects with
a common name can be a starting-point for reminding us of the Forms,
but it is not sufficient for knowledge of the Forms; rather, a productive
starting-point of classification assumes that it is an objective
classification contained in the Forms of which the classification of
particulars reminds us.
It is tempting to think of the Forms as perfect particular instances of
sensible objects. But this cannot be so. Plato was aware of this in the
“third man” argument: if all the instances of X are instances of X by
having in common some feature embodied in the Form X (Xness), and
the Form of X is itself an instance of X, then all the instances of X and
the Form of X taken together are instances of X only in virtue of some
further Form embodying common features in virtue of which all the
34 Greek philosophy
instances of X and the Form of X itself are X. And so on to infinity.
There is no doubt that the nature of the relation of the Forms to
sensible particulars presents Plato with difficulties, whether this
relation is said to be one of copying or resemblance, or one of
participation. If the relation is one of resemblance, there is the problem
revealed in the “third man” argument. If the relation is one of
participation, then we have the dilemma of deciding whether the Form
is present in each instance in its entirety or whether each has a
different part of the Form: in the first case the Form which is supposed
to be one or unitary is yet in its entirety in many individuals, in the
second case we lose anything common to, or the same in, all the
instances, and the Form is both one and many or divisible.
One way of thinking about the Forms is to consider them not as
entities which are perfect instances of sensible particulars, but more as
akin to formulae known by the intellect. This brings to mind the
Pythagoreans, for whom Plato had some sympathy. There is a
completely general formula for a circle, but the formula is not itself
circular or an instance of circularity; the formula may be verbal as “a
plane figure bounded by one line every point of which is equally
distant from a fixed point called the centre”, or as an algebraic
equation. In the same way the formula or definition of man or bed is
not itself an instance—even a perfect instance—of a man or a bed.
The main feature of Plato’s achievement is perhaps the way he laid
down the highest standards for knowledge as absolutely universal,
certain and necessary—a standard for which scientific knowledge has
striven. The standard is too high for natural science. Nevertheless, it
points scientific knowledge away from the particular case toward
unifying and inclusive truths of greater general explanatory power and
scope. Science does not deal with particulars, which in their full
particularity are unknowable, since the inevitable use of universal
terms means they can never be pinned down in their unique
particularity. Scientific knowledge deals with generally applicable
unifying truths concerning the underlying common or general features
of an apparently enormously diverse world. Thus it will concern itself,
at one level, not with this table and that table, or tables and cows, in so
far as they differ and are particular, but with giving a unified
explanation for their behaviour under their common nature or feature
of all being bodies or material objects. Science is concerned with the
structure or nature of an underlying general explanatory reality which
is fully objective and rationally understandable.
Aristotle
Aristotle (384–322 BC) was born the son of a prominent physician, in
Macedon in north east Greece. The medical interests of his family
Aristotle 35
encouraged his own later detailed empirical works in biology, which
influenced his philosophical outlook. At the age of seventeen he
became a student of Plato’s Academy, and later a teacher there. In the
early days he was generally in agreement with Platonic philosophy,
paying particular attention to the Phaedo, and only later, in important
respects, did he reject Plato’s philosophy. Nevertheless, he continued
to share Plato’s opposition to scepticism, and agreed that knowledge is
possible; it is on how the sceptical problem is to be solved that they
differed. Aristotle was predisposed to take a greater interest than Plato
in the natural world, of which Aristotle thought knowledge is possible.
Following the death of Plato, Aristotle left the Athenian Academy, and
was eventually tutor to the heir to the Macedonian throne, Alexander
the Great. Aristotle returned to Athens in 335 BC, and taught at the
Lyceum; but following the early death of the all-conquering Alexander,
resentment arose at the Macedonian domination of Greece and the
city-states; this made Aristotle’s position in Athens, as an alien with
Macedonian connections, increasingly uncomfortable. A charge of
impiety was brought against Aristotle; rather than be the central
character in a replay of the fate of Socrates, he left Athens in 323 BC.
Unable to return home to Stagira, the city of his birth, which had been
destroyed, he went to the remote city of Chalcis, where he died in
lonely exile in 322 BC at the age of sixty-two. He married twice, having
been once widowed; by his second marriage he had a son,
Nicomachus.
The philosophy of Aristotle owes a great deal to Plato. First,
although Aristotle rejected Plato’s theory of real separately existing
Forms, he held on to the notion of forms as the unchanging reality
providing the basis for knowledge proper of what things are. Plato’s
intelligible Forms are essences or defining formulae that really exist as
separate entities transcending the sensible world and minds.
Aristotle’s intelligible forms are immanent (in-dwelling) in sensible
particulars, and cannot, unlike Platonic Forms, exist apart from
particulars; the Aristotelean forms can be separated from particulars
only in thought, although they are objective and not subjective or
mind-dependent. Second, Aristotle supports anti-mechanical,
teleological methods of explanation. Teleology is not so much an
empirical hypothesis as a decision to adopt a certain method of
explanation. It aims to explain why things are as they are by referring
to the ends to which they aim; the end is being perfect, or fully
developed, specimens of the kind of things they are. It is reasonable to
see Aristotle as synthesizing Platonic realistic abstraction with a
concern to explain the natural world found among the Presocratics.
Aristotle agrees with Plato that knowledge proper or scientific
knowledge (epist¯em¯e) must be certain and necessary; knowledge is of
invariant or unchanging universal necessary truths. Knowledge must
be knowledge of something. Aristotle shares with Plato the notion that
36 Greek philosophy
if knowledge is possible, knowledge must be of what is real, and what
is real is eternal and unchanging. In short, the necessary truths we
know must be matched by their referring to ontologically suitable
objects.
Aristotle rejects Plato’s solution of positing as the true objects of
knowledge a realm of separately existing essences, the Forms: first,
because he thinks it only duplicates our problems concerning
knowledge of the world, and second, because Plato gives no clear
account of how individual objects in the world are supposed to
participate in, or resemble, the Forms.
Knowledge for Aristotle consists in a systematically connected set of
disciplines. Metaphysics (First Philosophy) is the most general and
fundamental aspect of all knowledge because it studies being qua
being. Unlike each individual science, metaphysics examines not this
or that sort of thing, but existing things, or being, as such; it restricts
itself to understanding that which is common to all and only things
which are real and have being; it studies those features of things which
they have merely in virtue of their existing as real things at all.
If the world is in constant flux, as Heraclitus suggests, then it cannot
contain eternal unchanging objects suitable for knowledge. If we
adopt, on the other hand, a Parmenidean view, all change and
plurality in the world are illusions, for they involve logical
contradictions: F becoming not-F; hotness becoming coldness.
Atomism may seem to point to a way out, for atoms remain the same
(have being) through change; indeed change is simply a rearrangement
of the same atoms. Aristotle rejects atomism (or materialism) because
collections of atoms do not do justice to our common-sense, or pretheoretical,
notion that there really are separately existing individual
instances of kinds of things. Atomism allows no distinction in kind
between a mere heap of bricks and a horse which is a genuine
substantial separable, hence bounded, kind of thing. Although a brick
may be an instance of a “so-and-so”, a heap of bricks is not identifiable
as a new “this so-and-so”. Matter alone is not a “this so-and-so” (it
does not pick out, say, this horse), for it is common in its nature to
different kinds of particulars, and thus cannot differentiate between
them as particulars of different types.
The important point is that the talk of the kinds of things there are
in the world which concerns Aristotle corresponds to real or natural
kinds; the way things are grouped together by kind, if properly
carried out, marks real objective divisions in the world made by
nature herself, not merely the arbitrary or subjective classification
into groups imposed by us on individuals which are in some way
similar.
For these reasons Aristotle posits substance as that which has
identity or stability through change. Aristotle notices that when we
talk about the world we distinguish between certain factors that alter
Aristotle 37
and certain factors to which the alterations occur which can remain the
same. Substances are, in a sense, pivots around which change occurs.
This is supported by the logical analysis of the carrier of all true or
false assertions about the world: the proposition. In Aristotle’s view
propositions always contain two elements: the subject and the
predicate. Predicates are what is said to be true or false of subjects.
Subjects can remain the same while having different, or indeed
contrary, predicates applied to them, and predicates logically depend
on there being subjects.
Predicates, whereby we say things about subjects, can be grouped
in different sorts or categories that are the highest genera or classes of
being and together may cover all modes of being. Aristotle gives the
ten genus categories as: substance, quality, quantity, relation (which
are the chief categories), place, time, less temporary condition/state,
more temporary condition/state, activity, passivity. Under the genus
category of relation, how something is related to other things, there is
among others the species of spatial relation, an example of which is: X
is to the left of Y. The metaphysical counterparts of subjects and
predicates are what these terms stand for. The most fundamental
category is that of substance; predication in this category tells us,
concerning the subject of a proposition, what kind of thing it is: X is a
horse. To say what kind of thing X is, is to give its essence; the other
categories of predication are of accidents, and these depend
ontologically on, and are always predicated of, substances. The
essence or “whatness” of a thing is given in a real definition or
formula which provides the necessary and sufficient conditions for a
thing to be what it is; an essence is what is common to all and only
things of a specific sort in virtue of which they are the sort of things
they are. This is a logically separate question from whether there
exist things of that sort: the existence or “thatness” of a thing. In
short, the essence refers to what it is to be an X; the existence refers to
the fact that there is an X; and one can know what an X is without
knowing that an X is. The essence of X therefore defines what we
mean by an “X”.
A term such as “horse” is a species substance term identifying a
species of a substantial separable way-of-being; a species quality term
such as “pale” is a non-substance term identifying a species of a nonsubstantial
non-separable way-of-being. In either case, contrary to
Plato’s theory of Forms, there cannot, metaphysically speaking, be
universal attributes such as horseness without horses or paleness
without some object or other that is pale. But whereas an instance of
the way-of-being of a substance never depends for its way-of-being on
its predication of any other way-of-being, the way-of-being of a nonsubstance
always depends for its way-of-being on its predication of
some other way-of-being. This indicates that the relation between
substances and accidental attributes is asymmetrical. It always makes
38 Greek philosophy
sense to ask, if any non-substance term such as “pale” is applied,
“What is it that is pale?”. It makes no sense to ask, if a substance term
such as “horse” is applied, “What is it that is horse?”. The logical point
about subjects and predicates, and the corresponding metaphysical
dependence of some ways-of-being on others, led Aristotle to
formulate two senses of substance.
(a) It must be that which is always a subject of predication, and never
predicated of any subject.
(b) It must be that which has an independent or separate way-of-being
or mode of existence.
What satisfies these formulations, and is substance in the primary
sense, is concrete individuals of various identifiable kinds that can
exist separately: they are those instances of whatness or ways-of-being
that have a separable existence. These are independent subjects which
can undergo certain changes while they remain identifiable as the
same kinds of individuals. Substances are still pools of being in a sea of
accidental becoming which avoid the conclusion that every change of a
subject of change is a change in the subject of change. The subject
Socrates can change from young to old, pale to flushed, and yet he
remains the same individual: an instance of a man. The Greek word
Aristotle uses for substance, ousia, is derived from “to be”: substances
are the most primary ways-to-be identifiable as “this so-and-so” (the
Greek is tode ti), of which all other ways-to-be are predicated modes,
and on which those other ways-to-be are dependent for their existence
as ways-to-be. Paleness as a way-of-being depends for its existence
both on some instances of paleness and on objects of some kind or
other being pale; but the instances of kinds of objects which are pale, if
they are substances such as this man, are not dependent on their being
predicated of instances of any other kinds of being.
Primary substances are not, however, the objects of science. Science
studies universal necessary features of the objects of the world, not this
or that object in its particularity. Aristotle supports the commonsense
or pre-theoretical view that individuals fall into determinate natural
kinds of things. Thus individual men fall into, and are instances of, the
natural kind man, and individual horses fall into, and are instances of,
the natural kind horse. Aristotle refers to the universal predicates that
define the properties that individual instances of a natural kind must
have in order to be the kind they are as substance in the secondary
sense: substance because they are the objects of science, secondary
because the being of a certain kind as such is dependent on there
existing individuals or instances of that kind. There cannot be
independent “so-and-sos”, or bare types as such, “floating” around,
unattached to particular “thises”; there cannot be the universal essence
horseness existing without there being particular horses existing. So
we have two meanings of substance:
Aristotle 39
(1) Primary substances: individual instances of the class of universals,
designated by a certain category of predicates, which can exist
separately being what they are—“this so-and-so”, this X, this man,
this horse.
(2) Secondary substances: the universals, designated by a certain
category of predicates, which are the properties defining real or
natural kinds or what something is, of which primary substances
are instances: “so-and-so”, Xness, man, horse.
Logically speaking, secondary substances are a special class of
predicates. The secondary substance predicates designate certain sorts
of property, the sorts of property which are the essential defining
properties of a thing that tell us what a primary substance is, and
which it cannot lose without ceasing to exist as the kind of thing it is.
In addition there are non-substances:
(3) Non-substances: the classes of universals and particulars,
designated by certain categories of predicates, which are not
capable of independent existence as identifiable instances of kinds
or ways-of-being—X, a heap of bricks; Xness, paleness.
The categories of universal predicates which identify non-substantial
dependent ways-of-being are accidental properties; these are properties
which a primary substance can gain or lose while continuing to exist as
the kind that it is, that is, while remaining the same identifiable kind of
individual.
In the case of (3), non-substances are not primary substances, either
because they are not capable of separate existence as instances of what
they are (for example, paleness) even though they may designate a
universal, or because they are not identifiable individual kinds or
ways-of-being at all (for example, a heap of bricks) even though they
are capable of independent existence.
A genuine substance must for Aristotle satisfy two conditions: it
must be both a determinate instance of a “so-and-so” or “whatness” of
some identifiable sort and also capable of separate existence as that
way-of-being such that it is not a modification or qualification of the
way-of-being of any other thing. A substance is both an individual
instance of a universal—an identifiable “this so-and-so”—and a wayof-being
that can exist separately, not as a mode of any other
identifiable “this so-and-so”. This man or Socrates satisfies both the
conditions for being a substance: it is both identifiable as a “what”—an
individual instance of man—and has a separate or independent
existence, is not a way-of-being dependent on the modification of any
other thing. In short, substances are the class of particular whatnesses or
ways-of-being that do not depend for their existence on being
modifications of any other thing or way-of-being.
Thus Socrates is a primary substance both because he is an instance
40 Greek philosophy
of the identifiable universal way-of-being man (unlike a heap of bricks,
which is not an instance of a universal way-of-being at all), and
because the way-of-being which is a man does not depend for its
existence on the modification of any other thing or way-of-being
(unlike an instance of paleness which depends for its existence on
being a mode of some other thing). An instance of paleness depends, in
a way that an instance of man does not, on there being some other
thing—for example, this man or Socrates—which is pale; logically
there cannot be an unattached instance of paleness without a subject
which is pale; there can logically be unattached instances of Socrates.
Primary substances are compounded of two elements,
(a’) matter (hyl¯e)
(b’) form (eidos, morph¯e).
By “matter” here is meant something more general than the physical
stuff out of which it is made; what is meant by “matter” is whatever it
is that takes on a certain determinate form, which thereby turns a
“this” into a “this so-and-so”. The form of a thing is immaterial and
structural, and it is what gives matter a determinate character as a
certain kind of thing. The form is the structure or shape the matter has
which makes it a determinate kind of individual or instance of a
kind—rather as there might be two brass keys (they are of the same
matter: brass), but only one fits my front door (they are of different
forms: shape). So matter is that which is “informed” as an identifiable
kind of thing, and form is that which makes some matter something of
a certain kind: the whatness, or being-what-it-is, of each individual. In
this sense any matter as such is potential substance, which is actualized
as substance when it takes on a form and becomes a “this so-and-so”.
The meaning of “matter” here is not restricted to physical stuff:
“matter” might be a man’s general character that takes on the form
“bad” so he has a “bad character”.
The connection between the secondary substances and the forms—
(2) and (b’) above—is that secondary substances are instantiated in
particular instances in matter as the form of that matter; the “so-and—
so” of a “this”, giving a separately existing individual, “this so-and-so”
of a certain kind or sort. The form or essence is what all and only
individuals sharing a common name and falling into a natural kind
(marking a natural division in nature such as horse) have in common
in virtue of which they are the kind of things they are. It perhaps helps
to understand what is meant by matter taking on a determinate form,
while also seeing that form is not a separate entity, to think of stone as
a petrifying of matter, and of a horse as an equinizing of matter.
Matter and form are the logical parts of substance (apart from God
who is pure actualized form); they always occur together and can be
separated only in thought; we never find “prime matter” devoid of all
specific determinations. Anything said of something posited as prime
Aristotle 41
matter would show it not to be prime, because the ability to talk about
it and say what it is would necessarily involve saying that it has some
specific characteristics or whatness. Prime matter is literally ineffable.
Specific compounds of matter and form are in a hierarchy of matter
and form; for what takes on a certain form will already have form at
some level. For example, a lump of bronze is matter with the
determinate form of bronze, and a bronze statue is matter with the
determinate form of bronze taking on the form of a statue. The same
bronze statue may be melted down and take on a new form, turning it
into a bronze bowl. With the progressive addition of form to matter we
can move “upward” from clay, to bricks, to walls, to house. That
matter and form are logically distinct is shown by the fact that we can
have the same form giving an instance of a kind of thing (a hammer)
but different matter (some metal, some wood), and have the same
matter (some metal) but a different form giving an instance of a kind of
thing (a hammer, a chisel).
These distinctions allow Aristotle to give an account of change. He
distinguishes two sorts of change:
(a’’) substantial change
(b’’) non-substantial change, or accidental change.
These mark the distinction between (a’’) cases where a new kind of
individual comes into being and (b’’) cases where the same kind of
individual thing persists in being through change. As a man moves
from being young to being old we have a case of non-substantial
change; the subject of change remains, through the change, the same
individual or instance of what kind of thing it is: a man. But when a
man dies, we have a case of substantial change—the individual
becomes a different kind of thing. What it is is something else: a mere
pile of flesh and bones. The form or essence of a thing X is a core set of
properties a, b, c, which are together necessary and sufficient for X to
be the kind of thing it is; that is, properties that jointly all and only
things of kind X have that thereby determine what they are. What
remains the same through substantial change (a’’) is the matter (a’)
which has lost one form (b’) and taken on another form. What remains
constant through non-substantial change (b’’) is the form (b’) or
essence, formulated in a definition, that gives those properties that
make a thing the kind of thing it is.
Another way of looking at this analysis of change is to make the
distinction between the essential properties ((2) above) of things and
the accidental properties ((3) above) of things; so these correspond to
the secondary substances and the non-substances respectively. The
essential properties are those properties that remain the same through
accidental change whereby an individual remains in existence as the
same kind of thing or what it is. Essential properties are the properties
which are necessary and sufficient for an individual to continue to be
42 Greek philosophy
an individual of a certain kind. The essential properties are given by
the true or real definition of the term designating the kind of thing an
individual is: so something is of kind X if, and only if, it has properties
a, b, c; and this is the same as giving its form. The form of a thing is its
essence given by a real definition, and this remains the same through
accidental change. Thus a man can be hairy and go bald; he can change
his blue shirt for a green shirt; but he still remains a man, since
hairiness is not part of the definition of man. What is part of the
essence of a man, given by the real definition of man, is the set of
properties common to all and only individual men that makes it
correct to include them under the term “man”. Thus the real definition
of man, revealing his essential nature, may be “mortal animal capable
of discourse”, which is definition by genus (animal) and difference by
species (capable of discourse). The essential nature, or form, of a
determinate kind is the residue of features which remain after the
differences between individuals of the same kind have been removed,
and we are left with a set of properties that all and only individuals of
that kind have in common; in that way we say what some thing is.
How individuals of the same natural kind are to be distinguished is
a difficult question. They cannot be distinguished by their kind, since
that is common to them. One suggestion is that they are distinguished
by their parcels of matter, which will be different parcels in each
individual. Another suggestion is that we should admit individual
essences as well as essences by kind. Later philosophers have said that
only a complete enumeration of attributes of a given individual,
denying any distinction between those that are essential and those that
are accidental, can give a satisfactory principle of individuation.
Generally it is held that, for a principle of individuation to guarantee
unique reference, some appeal to space, time and motion is required.
To complete Aristotle’s analysis of the nature of change, we have to
make the distinction between “actuality” and “potentiality”. When
matter takes on a certain form, there is contained within the nature of
the form not only what the actual form is at any given time, but also the
potential further actualizations. For example, an acorn has a certain
determinate actuality (actual state) at any given time; but it is also
potentially an oak tree. Thus a complete characterization of the form of
a thing—determining what kind of thing it is—will include a
description of various progressive stages of actualization, and the full
actualization towards which that kind of thing aims, which it contains
only potentially until it reaches that end point. So a specimen of a
certain kind will be a compound of matter and form, and the form will
include what is actualized at any given time, plus its future potential
states. This process is particularly obvious in the case of a living
organism; but what it means in the case of non-living things is less clear.
The point to be noted is that the form limits the way that a particular
kind of thing goes on; acorns do not develop into horses, but have a
Aristotle 43
certain natural course of development. An eye that is blind suffers from
“privation”, because it is not actualizing its potential; whereas to say
that a tree cannot see is not to say it suffers from privation, since to
actualize seeing is not a potential part of the form of a tree.
Natural kinds are divisions of nature herself, not divisions imposed
arbitrarily by us in language; the divisions are discovered, not created.
How many different natural kinds there are is a difficult question for
Aristotle, and his answers are not always consistent, (i) The criterion
sometimes emphasized for natural kinds is that they are those things
that persist through change. In this case it seems to make sense to
include artefacts like beds in the list of kinds; a bed remains a bed after
it has been painted green instead of blue. (ii) At other times the
criterion emphasized is that of independence from external causes.
Thus sometimes Aristotle includes in the natural world only things
which can reproduce themselves “after their kind”: horses naturally
beget other horses, whereas if you plant a bed, you do not get another
bed produced, it has to be made. Also bits of stuff like pieces of wood
are excluded from the list of natural kinds since they are
indeterminate—they are subject to destruction by degree; whereas it
makes no sense to say of a horse that it is more or less a horse—it is
either a horse or not a horse.
The explanation of change is, however, sometimes very unclear. This
is partly due to difficulties as to what natural kinds there actually are.
It is also due to the obscurity of the distinction between essential and
accidental properties. This produces the problem of distinguishing
substantial from accidental change. If, for example, we have a change
of property from f to g, it may not be clear if it is correct to say, “Xf has
become Xg” (an accidental change), or if it is correct to say, “Xf has
become Yg” (a substantial change). If sweet wine turns sour, it is
unclear whether it is correct to say that the sweet wine has become
sour wine (an accidental change), or that the wine has become vinegar
(a substantial change). How are we to distinguish a change in
substance, a change from “this so-and-so” to a different “this so-andso”,
from a merely accidental change in the same “this so-and-so”?
There is a danger that if the number of instances of secondary
substances increases, the explanatory power of explanations which
depend on referring to the kind of thing something is will be
diminished. If, at the limit, every change of properties involved a
change in kind, then we would be unable to explain the change in
terms of its being a consequence of the properties of the constant kind
of thing in question developing in its natural ways, according to its
form or nature.
The point that this talk of natural kinds is leading to is that the
explanation for why a thing is as it is can be derived from discovering
the kind of thing that it is and its connection with more general natural
kinds of things. The form of a thing is an intelligible form; it is
44 Greek philosophy
ultimately perceived not by the senses, but by the intellect or reason—
by intellectual intuition (nous). It is this reference to the kinds or sorts of
things there are in the world that is the basis for scientific knowledge
and explanations of the world.
Knowledge is knowledge of “causes”, and Aristotle gives four
senses to the notion of “cause”. It is important to see that “cause” here
has a wider connotation than our mechanical notion, and none of
Aristotle’s four senses really matches our use of the concept. When he
is referring to understanding the causes of things, he is concerned with
providing an answer to a “why” question: “Why is X as it is?” There
are various ways of answering this question through different
“becauses”. This is not at all mysterious if we consider the way we use
non-mechanical explanations every day. Question: “Why was Durham
Cathedral built?” Answer: “Because people wanted to praise God.” So
Aristotle distinguishes four “becauses” answering “Why is X as it is?”:
(a) Material
(b) Formal
(c) Efficient
(d) Final or Teleological
The (a) here refers to the matter or stuff (not necessarily physical stuff)
out of which X is made. (b) refers to what kind of thing X is; it is a “soand-so”.
(c) refers to the agent (not what the agent does) that brings X
about. (d) refers to what X is for, or what its goal or end state will be;
what its purpose is. If we take the case of a house, we can see that (a) is
the bricks out of which it is made; (b) is the kind of house it is
(Victorian style terrace); (c) is the men who built it; (d) points to its
purpose of providing shelter. It should be noted with reference to (c)
that causal links, or “becauses”, hold for Aristotle not between events,
but between things. Taken together, these four causes provide a
complete explanation for why X is as it is.
In the case of things with final causes, the formal and final causes
will be closely linked; in giving the form of something, it will be
necessary to refer in a definition to what that something is for. The use
of form and function in explanations allows us to see why something
can remain the same thing, even when certain changes are made to it.
If a green bed is painted blue, it remains the same as an individual
instance of bed, in that its form and final “becauses” are unchanged.
We can plainly see that formal and final explanations are more
obviously applicable to artefacts and living organisms than to
inanimate objects. Aristotle suggests that stones fall down because
their natural place—their natural final state spelt out in their form or
essence—is as near to the earth as possible. But we would hardly
regard this explanation as satisfactory today. There is the danger that
explanations derived from the kind of thing X is in this way become
uninformative and lead us to fail to seek the real internal causal
Aristotle 45
mechanisms that bring about a specific change. We have not
identifying the object before us as a clock. The explanations are at risk
of being uninformative because they become tautological: X is as it is
because of the real definition of X, and any counter-evidence is
immediately excluded because if a putative X is found to act in a way
contrary to its definition then it is not a case of X at all. We cannot
define a thing if we exclude its causal powers; we thereby risk circular
explanations if causal consequences are deduced from definitions.
All substantial change involves matter taking on a new form, which is,
in some way, passed on from an agent. In the case of a house, the efficient
cause operates by the form of the house that exists as an idea in the mind
of the builder being passed on to the matter of the house. In the case of
natural objects, the efficient cause is the natural parent in which the form
of the offspring is latent. This logically rules out both creation from
nothing—where there is no matter—and any possibility of Darwinian
evolution of the kinds of things there are, since the forms manifested in
natural kinds do not change in themselves. God is the supreme source of
all change; He transcends the world as pure form devoid of matter, fully
actualized, possessing no potential. God is not the creator of the world
out of nothing, but the “unmoved mover” in the sense of a final cause
which is the ultimate cause of whatever form the world has.
Knowledge proper requires that its objects must be both really
existing, and eternal and unchanging. If nothing in the sensible world
is eternal and unchanging, then it follows that knowledge of the
sensible world is not possible. If it is also the case that the sensible
world is the only really existing world, then knowledge is not possible
at all. If knowledge is possible, but it is accepted that the sensible
world is not eternal and unchanging, then knowledge must be of a
really existing transcendent supersensible world of eternal and
unchanging objects: the Forms or essences of Plato. If knowledge is
possible, but it is accepted that the sensible world is the only real
world, then knowledge must be of really existing eternal and
unchanging features of the sensible world: the forms or real kinds of
Aristotle. That is, if knowledge proper is possible, it must be the case
either that there is a world of eternal and unchanging real objects
beyond the sensible world (the position of Plato), or that there are
eternal and unchanging real features of the sensible world (the
position of Aristotle).
Aristotle holds that there is something about the sensible world that
is eternal and unchanging and graspable ultimately by the intellect and
is a suitable object for scientific knowledge: the natural kinds of things
there are and the relations between them. These natural kinds are
objective really existing features of the world, not mere arbitrary
conventional classifications imposed by us. The common-sense view of
the world is that it divides itself up into many distinct kinds or sorts of
individuals; and we have knowledge proper or scientific knowledge
46 Greek philosophy
(epist¯em¯e), as opposed to mere belief or opinion (doxa), of those
individuals through knowing the kind of thing an individual is. It is
natural or real kinds that are the proper objects of knowledge.
Aristotle made great contributions to logic, which he sees as the tool
(organon) of philosophy. Through the notion of the syllogism he sought
to identify all the valid forms of deductive reasoning. In fact there are
other forms of deductive reasoning that Aristotle does not consider.
Deductive logic is a vital tool of philosophy, and of inquiry generally,
in providing a way to get infallibly from true premises to true
conclusions. If the premises are true in a valid deductive argument,
then we know that it must be the case that the conclusion is true.
Aristotle introduced the important notion of variables—letters such as
A, B, and C—to stand for classes of things; this reveals that deductive
arguments are valid or invalid regardless of their content and in virtue
of their argument-form. For example:
This is a valid argument-form: an inference which would be valid
regardless of what classes of things are substituted for A, B, C.
Aristotle ideally sees knowledge as forming a system that is a
deductively connected body of truths. Scientific knowledge is
knowledge of causes: giving the reason why X is as it is, and must be as
it is. We have first to know what kind of thing X is, and then to show
why, given the kind of thing it is, X must be as it is. Thus knowledge of
some truth about X would consist of deducing the truth about X from
premises which we know are true, thereby proving by a valid deductive
argument that what we say is true about X is necessarily true of X.
Aristotle was aware of an important problem connected with this:
all knowledge cannot be a matter of providing a deductive proof or
demonstration, because this leads to an infinite regress of proofs: any
premises we suggested would themselves stand in need of further
proof. If the regress is infinite, then nothing can actually be proved,
and nothing therefore known. This leads Aristotle to the view that
there must be self-evident first principles or axioms that can be known
immediately by intellectual intuition (nous), which neither require nor
are capable of proof. The most general and firmest of these principles
is the law of non-contradiction, which in the Metaphysics Aristotle
states thus: “For the same thing to hold good and not to hold good
simultaneously of the same thing and in the same respect is
impossible.” This can also be expressed in a more modern way: “It is
not the case that both p and not-p”, where p can be any proposition.
This principle is presupposed in all rational thought; thus any attempt
to prove it by rational thought is hopelessly circular. We can, however,
Aristotle 47
prove it by rational thought is hopelessly circular. We can, however,
simply see intrinsically that it is a true principle.
Ideally the deductions of science would take place from the most
fundamental first principles; but, in fact, this is not possible; science
cannot proceed purely a priori, independently of experience, because the
most general first principles are too general for studying particular
kinds of things. The deductions of science are based on real forms (the
essences, real natures) of things and true universal principles (all As are
Bs) connecting these forms; and the process of apprehending both of
these is initiated by induction. We observe by sense-perception many
particulars of the same kind, and through reason or intellectual intuition
(nous) we “perceive” the form or essence of that kind of thing as a real
definition or concept given by genus and difference. We then form a
hierarchy of different degrees of generality, of kinds of things,
descending to infima specie: those specific kinds of things below which
there are no further kinds, but only individuals of a specific kind. Such a
species would be man, and above it, and including man, is the genus
animal. We also derive in the same way, by sense-perception and
intellectual intuition, universal principles logically connecting the forms
or essences. We are able to have knowledge proper since, by taking the
forms and universal principles together, we are able to deduce universal
certain necessary truths about the kind of things we are interested in.
In this way it is shown why things are as they are, and why they
must be as they are, and not otherwise. If a certain truth about the
world is the conclusion of a valid deductive argument whose premises
we know to be true, we have shown: (a) why that conclusion is a truth,
because it follows logically from known premises, and (b) that the
conclusion is a universal necessary truth, in virtue of the argument
being deductive. To follow a valid deductive argument from true
premises is to follow a causal connection in the world. We explain
some feature of the world by deducing it from the definition of the
kind of thing it is and from principles universally true of a general
kind of which it is a part.
We might ask why X is f. If we know the kind of thing X is—it is of
kind Y—and the universal principle that “all Ys are f”, then we can
deduce and explain, why X must be f.
For example: “Why does a horse suckle its young?”
48 Greek philosophy
The principle in the second line is what science seeks to use in
explanations, and it is known only by inductive observation of many
animals combined with the use of reason or the intellect. The first line
is known in the same way.
Science—knowledge in its highest sense—deals with universal
eternal necessary truths, not with particulars as particulars. The
forms or essences of kinds of things, and the universal principles
derived from the connection of those forms or essences, are the real
eternal unchanging intelligible aspects of the world. For science to
study what is real there must be kinds or sorts of things that mark
real, objective, fixed cleavages in the world, which are not the
imposition of human conventional classification. That they are real
is an assumption Aristotle makes on the basis of our common-sense
ways of talking about the world. Our explanations derive from the
ways that the vast plurality of things of certain real kinds behave,
given that their forms or essential natures determine the kinds they
fall into. The positing of such fixed intelligible forms is what makes
a scientific knowledge of nature possible, in the sense of knowing
universal necessary truths about universal necessary features of the
world. Scientific knowledge gives deductive proof that specific kinds
of things are necessarily as they are. The common principles of all
reasoning, plus known universal principles, plus knowledge of the
kind of specimen we have before us, together enable us to prove
necessary truths about that specimen. It is possible for us to have
scientific knowledge of the world, since the world can be
understood according to general principles and real definitions
which do not alter and are eternal, and which the intellect can
apprehend.
It must be noted that this means that science can deal with
particulars only in so far as it considers them instances of universals; it
considers only objective universal properties common to all and only
particulars of the same kind. Science is concerned not with what
makes a thing particular, but with what makes it an instance of a
general kind. Science can have as its object only genera, species or
universals—the specific defining form that individuals share—and not
particulars as such. Individuals are in the scientific sense unknowable;
in their unique particularity they are perhaps ineffable, since to talk of
them at all is to use common classifying terms which apply to other
individuals.
While we might grant that the proper principles or laws that
science aims to discover are universal in application, we do not
thereby have to agree they are necessary. The inductive inferences as
envisioned by Aristotle to derive general principles concerning kinds
of things would at best be known to be universally true. Even this is
clearly not possible if the number of kinds in the class to be
investigated is infinite. However, Aristotle thinks that such induction
Aristotle 49
produces evidence supporting universal necessary truths which
intellectual intuition apprehends as necessary. The problem is that
this tends to confuse contingent universal truths—which might be
supported, if not conclusively, by experience—with necessary
universal truths which are necessary just because their truth is
independent of all experience and which rely for their necessity only
on logic and the meaning of their terms. Aristotle relies on the
justification of intellectual perception—going beyond the limited
possibilities of experience—to establish finally the features of the
inmost nature or essence of things, the correctness of our real
definitions of those things, and the necessity of principles. But it is
not clear that an account of there being necessary truths depends on
the subjective intuitive self-evidence of some truths, rather than on
the purely objective logical form of such truths, such as the denial of
a necessary truth implying a contradiction. Moreover, if the necessity
of a truth is entirely a result of its denial implying a contradiction,
then it does not say anything about an actual world if the nature of
that world is not logically necessary but contingent; then truths
about that world cannot be known to be true merely by showing that
their denial implies a logical contradiction, because none of them
does.
Plato and Aristotle think that science should attain knowledge of
universal necessary truths. Aristotle thinks we can have scientific
knowledge of the sensible world because eternal unchanging forms
are immanent in the world of sensible objects. The sensible world
thus has two aspects: its sensible aspect, and its intelligible aspect
(the forms), and we can, through the intelligible aspect, know
necessary truths about the sensible world. That such provable
universal necessary truths—propositions whose falsity is
impossible—are restricted to mathematics and logic is now
something generally accepted to be the case. Plato, we might say, was
more aware of this point in thinking that if knowledge (epist¯em¯e) of
necessary truths were possible it must be of a supersensible world,
not of the empirical world. Plato thinks that the universal necessity
of the truths of highest forms of knowledge depends upon their being
about eternal transcendent supersensible objects beyond the natural
world: Forms, essences, or objective concepts. Whether such realism
is required to account for knowledge of universal necessary truths is
certainly disputable. It might be possible to account for necessary
truths without saying that they are about any world of real objects at
all, perhaps by saying that they are merely those propositions whose
denial implies a contradiction. Plato disagreed with Aristotle who
thought that knowledge, even in the highest sense of knowledge of
universal necessary truths, must be about aspects of the world of
sensible or empirical objects. The point at issue here is whether there
is such a thing as natural necessity: whether there are necessary
50 Greek philosophy
features and connections in the natural world expressible in
necessary truths, or whether such necessity is restricted to logical
truths which say nothing about the natural world, although they may
say something about a world of real objects apprehended by pure
intellectual thought beyond the natural world.
Aristotle 51
continued to ...