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CHAPTER THREE
Medieval philosophy:
Augustine, Aquinas, Ockham
In thinking of medieval philosophy, we must consider that we are
covering a vast time of around a thousand years including St
Augustine of Hippo (AD 354–430) and William of Ockham (c.1285–
1349) and extending until at least the time of the Renaissance. What
links the diversity of this period in Western philosophy is the rise to
dominance of Christian beliefs.
It would be wrong to conclude that thinkers in the medieval period
merely slavishly reiterated Christian dogma. There exists a tension in
medieval philosophy between reason and faith (from the Latin fidere,
to trust). The distinction, if there is admitted to be one at all, between
the reason of philosophy and the faith of theology is that between,
respectively, the insights of natural knowledge derived from the
natural cognitive powers of the intellect and senses, and the insights of
supernatural knowledge derived from divine revelation. The
distinction between philosophy and theology in the Middle Ages was
often not clear; generally it can be said that whereas philosophy
embodied rational arguments based on premises derivable from
naturally occurring powers of thought and the logical working out of
those premises (particularly from the philosophers of the ancient
world, especially Aristotle), theological arguments were based on
divine Christian premises derived from God—in particular from the
Bible and the opinions of the Church Fathers as collected in Peter
Lombard (c.1100–60), Four books of sentences. Christian thought insisted
that reason must succumb to the deliverances of faith or religious
belief where the two are irreconcilable.
It is characteristic of the dominant intellectual framework of the
scholars of the universities of the medieval period—called scholasticism—to
try to reconcile the demands of rational philosophy and the
demands of theological faith. The dissolution of scholasticism at the
end of the Middle Ages really amounts to the increasing triumph of
reason over faith; instead of Christian faith being the standard by
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which rational arguments were to be judged, arguments were
increasingly followed wherever they led. Reason in scholasticism was
often used as a tool for supporting and deepening the understanding
of what was already believed to be true as a matter of religious faith.
After all, it is reasonable to suppose that even if some true beliefs are
accepted as true without sufficient argument, it might still be possible
to provide a rational justification for those true beliefs.
It was also thought that some truths were beyond the reach of
rational demonstration, but that this was not detrimental to these
truths, since their acceptance depended on religious faith. Belief in
truths of faith influenced rational arguments by affecting the premises
considered, and by judging the truth of the conclusions reached. If a
valid argument leads to a conclusion which is false—false, in this case,
according to religious faith—we know that at least one of the premises
must be false. However, the strain of combining reason and faith
eventually led to the separation of philosophy and theology; the
attempt had been made to fit philosophy in as a rational, but limited,
path to religious truth, but in the end it tended to undermine the body
of theological dogma.
The source of medieval theological doctrine was the Bible and the
Church Fathers; the problem presented to medieval thinkers was how
to reconcile beliefs from these sources with the beliefs and logical
arguments derived from Plato and Aristotle, and the attempts of
Arabic and Jewish thinkers from the tenth century to the twelfth
century to combine Plato and Aristotle. This reflects the high opinion
which was held of work from the ancient world; throughout the
medieval period, ancient philosophy was a source of authority which
toward the end of the period was used to oppose new arguments in
philosophy and science. Nearly all medieval philosophical literature
takes the form of either commentaries on previous works (especially
Aristotle), or disputes (quaestio disputata), where a question would be
raised and opposing solutions and objections considered and
eventually reconciled.
During the period from the second century to the fifth century AD,
while the Roman Empire remained intact, Platonism and
Neoplatonism had the upper hand in Christian thought; this is
apparent in the works of St Augustine. The greatest Neoplatonists
were Plotinus (AD 205–270), his disciple Porphyry (AD 233–304), and
later Proclus (c. AD 410–485). St Augustine adopted, but profoundly
modified, Platonism in the service of Christianity, to which he
converted in AD 386 at the age of thirty-two. But with the break-up of
the Roman Empire in the fifth century, Western Europe and the eastern
parts became separated, and from the sixth century to the eleventh
century we enter the Dark Ages.
During the Dark Ages nearly all serious intellectual activity ceased
in Western Europe, although it continued in the eastern provinces
Augustine, Aquinas, Ockham 53
conquered by the Arabs. From the fifth century onwards little of Plato
was known directly in Western Europe, and the full corpus of his
works did not re-emerge until the end of the Middle Ages; apart from
in the work of John Scotus Erigena (c.810–c.877) Neoplatonism as such
was also not rediscovered until the late twelfth and thirteenth
centuries, but its influence seeped in from around the fifth century
from the Arabs and the works of Pseudo-Dionysius, who was falsely
thought to be the Athenian converted by St Paul. Only the works of
Aristotle on logic remained known throughout the Middle Ages,
thanks largely to translations and commentaries by the Roman
philosopher Boethius (c. AD 480–524); but in the latter part of the
twelfth century other works of Aristotle were rediscovered, revealing
the ambitious system of metaphysics, science, and ethics.
In contrast to the period before the lacuna of the Dark Ages, after
that period it was Aristotelian philosophy, rather than Platonic
philosophy, which dominated Western European thinking. It was
during the period from the twelfth century to the fourteenth century
that the tensions between reason and faith intensified, and this gave
way to the progressive weakening, from the fourteenth century, of the
scholastic attempts to harmonize the two. The spread of new ideas
continued, aided by the invention of printing in the fifteenth century.
Intellectual changes were matched by the disintegration of the
medieval social order; the increased disrespect for ecclesiastical
authority and the rise of the rival power of the nation state
undermined the unity of Christendom. The door was open for the
Protestant Reformation of the sixteenth century and the greater
importance of the conscience of the individual and direct
understanding of Christianity. Philosophy became increasingly
autonomous after the fourteenth century, and the gap between
philosophy and theology was never again closed. By the end of the
medieval period both Christianity and Aristotelianism, as the
authoritative storehouses of correct opinions, were being replaced by a
different vision of intellectual and moral advancement in the light of
new philosophical and scientific ideas.
Given such a long period as the Middle Ages, it is unsurprising that
it is possible here to make only a small selection of its thinkers. Apart
from the thinkers discussed, among other important figures are
Abelard (1079–1142), St Anselm (1033–1109), St Bonaventure (1221–74)
and Duns Scotus (c.1266–1308). Augustine, Aquinas and Ockham are
chosen here as representative of different important aspects of the
period; they might be said to embody respectively medieval
philosophy’s inception, its consolidation, and the beginning of its
dissolution. Their views on the place of reason and faith can roughly
be summarized as follows: for Augustine there is no fundamental
distinction because reason depends on divine help to grasp eternal
truths; for Aquinas there is a distinction on the basis of the natural and
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the divine but the two are complementary and to a degree
overlapping; for Ockham reason and faith are distinct and have no
overlap.
Augustine
Augustine (AD 354–430) was born in Thagaste and died in Hippo, both
places in North Africa. Intellectually he straddles the gap between the
philosophers of ancient Greece and those of medieval Christian
Europe; he lived through the decline of the Roman Empire, which led
to the Dark Ages. The eventual historical outcome in the eleventh
century was the increased dominance of Christianity. Augustine’s
mother, Monica, was a Christian, but initially he did not accept the
faith and adopted Manichaeanism, which embodied some elements of
Christianity among elements from other religions. At the age of
seventeen he became a student of the University of Carthage where he
became a teacher of rhetoric and, while there, lived a life of
extravagant pleasure—including sexual pleasure—which was to
contrast starkly with his later monkish life. In AD 383 he moved to
teach in Rome; following financial problems, he accepted a teaching
post in Milan, where he greatly augmented his knowledge of ancient
Greek philosophy, in particular Neoplatonism. In Milan he was
impressed by the teachings of Ambrose, Bishop of Milan.
Augustine converted to Christianity in AD 386, and was baptized
the following year. He was then determined to enter the Church and
renounced worldly pleasures. Initially Augustine found no difficulty in
reconciling the dominant intellectual position of his day,
Neoplatonism, with the demands of Christian scripture; later he began
to see greater problems in reconciling their basic concepts. He soon
founded his own monastic community in Thagaste; but this lasted only
a couple of years through his being forced into the Catholic priesthood.
Augustine eventually became Bishop of Hippo in AD 396. He never
left North Africa for the last thirty-nine years of his life. In AD 410,
Rome was sacked by the Goths; in 429 the Vandals crossed to North
Africa from Spain and laid siege to Hippo; Augustine died in 430, aged
seventy-five, a short time before Hippo fell.
The character of Augustine’s thought is distinctly religious, rather
than purely philosophical; the discussion of certain philosophical
problems is not that of the disinterested academic, but has the
overriding purpose of identifying the path to the attainment of
blessedness or beatitude. This does not mean that what is true is
crudely identified with whatever makes one happy; it is rather the
other way around: knowledge of truths will make one happy. It is
assumed that the wise man and the happy man are one, and
knowledge of truths is part of the attainment of wisdom. The question
Augustine 55
of whether we can know truths is generally assumed to be answered
positively; the chief question is how we can attain that knowledge. The
overall religious purpose is twofold: first, to show how we can become
closer to God; secondly, to emphasize the importance of God by
showing how everything is closely dependent on God.
A problem of particular concern to Augustine is how we come to
know the universal necessary eternal truths described by Plato and the
Neoplatonists. First, however, Augustine sets about demolishing the
sceptic who asserts that no knowledge at all is possible. He points to a
range of things we clearly know to be true, which the sceptic cannot
possibly deny. He is not aiming to use these known truths as the
axiomatic foundation of the rest of knowledge, rather, if any of the
examples are admitted as known truths, then knowledge is possible,
and the absolute sceptic refuted.
(a) We know the law of non-contradiction, whereby if something
is true, it cannot also be the case at the same time that the
opposite is true.
(b) I know that I exist. “If I err, I exist” (“Si fallor, sum”). This
anticipates Descartes’ cogito; but it is not used in the same way;
Augustine is not concerned to use it to prove the existence of the
external world.
(c) Appearances cannot in themselves be false; I know infallibly
what my subjective experiences are, how things appear to me: my
“seemings”. I can know infallibly what seems to be the case; it is
my judgement, which goes beyond what seems to be the case,
which introduces the possibility of falsehoods.
(d) We clearly, even from the sceptic’s point of view, have the
capacity to doubt; so we know at least one truth: there is
doubting.
(e) We obviously know with certainty mathematical and geometrical
truths.
(f) We do not just know abstract principles, we also know real
existences. We know that we exist, that we are alive, and that we
understand these facts. Augustine points out that even if our
experience is really a dream, we nevertheless still know we were
alive. We are also conscious that we will certain things.
These bulwarks against scepticism are in one way or another derived
from introspection independently of the errors of the senses.
Augustine does not dismiss the senses as wholly deceptive. From the
fact that we can sometimes err in our sense-based judgements (for
example if we judge that a stick which appears bent in the water really
is bent), and can on any particular occasion err, it does not follow that
the senses cannot ever support true beliefs. That the senses deliver
truths less certain than those of mathematics does not mean the senses
do not deliver truths at all. However, Augustine supports the Platonic
56 Medieval philosophy
view that the lack of certainty and the relativity of judgement (the same
thing can appear different to different people) that beset the senses
make the objects of sense not suitable objects for true knowledge or
knowledge proper. The true objects of knowledge—the truths we can
know with greatest certainty—are truths that are universal, necessary,
and eternal; this is the highest form of knowledge, and sensory
knowledge the lowest. This means that these eternal truths have to be
found within the mind independently of sensory experience.
The problem arises of how eternal truths and our knowledge of
eternal truths are to be accounted for. The sensible world does not
provide us with the required immutable concepts and truths; the
human mind or soul, although immortal, is also temporal and
mutable. Augustine agrees with Plato that, just as transient truths are
accounted for by the mutable objects of the sensible world, so
universal necessary eternal truths are accounted for by their being
truths about eternal and immutable real objects. Moreover, these
eternal objects, and the truths concerning the relations of the concepts
of these objects, are independent of the human mind; they are truths
that we discover, which we cannot alter, and which are thereby
objective and common to all capable of reasoning. Such objects—
immaterial impersonal essences—referred to by Plato as Forms, are
identified by Augustine as ideas in the eternal, immutable mind of
God—they are the content of the divine mind. Such divine ideas
provide both truly objective fixed concepts and necessary truths by
being the objects of necessary judgements. Augustine, like Plato, has
no facility to account for the necessity of some truths which does not
involve realism, requiring there to be eternal objects to which those
truths correspond; he is unable to account for such necessary truths
merely on the basis of the logical relations between concepts, but
thinks that such truths require eternal objects which the eternal truths
are true of eternally.
Such necessary truths are available to us in the areas of mathematics
and geometry, but they are also possible in moral and aesthetic
judgements. The divine ideas provide perfect objects for the concepts
of number and geometrical forms; they also provide objective
standards for moral judgements concerning good and evil, and
aesthetic judgements concerning what is, or is not, beautiful. We do
not find perfect unity in our experience (we always find things with
parts which are thereby both one and many); we do not find absolute
goodness or evil or perfect beauty in our experience. We do not find
these things in themselves exemplified in the sensible world; but nor
are they mere constructions of the human mind. Rather, the divine
ideas in God’s mind are the absolute eternal standards by which all
else is judged, and which are assumed in our judgements.
The problem remains of how such eternal truths are accessible to the
non-eternal human mind. We have certainly been granted reason by
Augustine 57
which we are able to form true or false judgements not derivable from
sense-experience. But reason alone is not enough to account for our
knowledge of eternal truths. The human mind, in seeking eternal
truths, is seeking something beyond, and superior to, the mutable and
temporal mind, and to know such truths we need help. Such help
emanates from God in the form of “divine illumination”; and as an
illuminator God is present in us as He is present in all things. All
knowledge in Augustine is seen as a form of seeing. Just as the senses
see independent objects when they are illuminated by the sun, so
reason or intellect “sees” eternal truths when illuminated by the divine
light. This does not mean that in apprehending eternal truths we have
direct access to God’s nature—that is possible only after death, if at all.
We do not intellectually see God or the mind of God when we know
eternal truths. It is unclear whether the illumination implants the
concepts constituting necessary truths in our minds, or whether it
simply enables us to recognize which judgements are eternal and
necessary—it could indeed function in both ways. Perhaps the best
interpretation is to say that God does not directly infuse our minds
with the absolute concepts which constitute eternal truths, rather such
concepts are latent in the mind as copies of the archetypes in God’s
mind; divine illumination enables us to see intellectually which are the
eternal and necessary truths that are latent in our souls, and so to
recognize them as eternal and necessary. The latent concepts, and the
eternal truths connecting them, are in memoria; in this way ideas can be
in the mind without the mind being aware of those ideas. This accords
with our use of “memory” only in that it refers to ideas that can be in
the mind without our being always aware of them; it refers in
Augustine, most importantly, to the a priori content of minds, which is
not literally a remembrance of things past. Nevertheless the theory is
close to Plato’s account of our possessing a priori knowledge through
reminiscence.
Eternal truths are, of course, independent of and irrefutable by
sense-experience. So the true objects of knowledge are objective eternal
objects which depend on there being ontologically appropriate eternal
objects in the divine mind. Knowledge of eternal truths is granted by a
combination of natural human reason and supernatural divine
illumination. To benefit from such illumination we have to turn
towards God. This precludes the possibility of making a distinction
between natural reason and divine faith, for both are always needed
and mixed in the search for knowledge. This again emphasizes the
dependence of all things on God, in this case our capacity to know
eternal necessary truths.
The immateriality of the soul and its superiority to the body mean
that Augustine has great difficulty accounting for perceptions through
the corporeal organs. The superior nature of the soul’s mode of
existence involves the view that it cannot be affected by the inferior
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corporeal organs. At first he suggests that the mind uses the sense
organs as a tool. Later he tries to account for our awareness of changes
in our corporeal senses by the mind attending to or noticing such
changes; but it is difficult to see how, in this case, some causal
influence of the corporeal sense organs on the mind can be avoided.
Augustine uses the existence of eternal truths as proof of the
existence of God. Leibniz in the seventeenth century presents a
similar argument. The argument starts by getting one to admit that
there are eternal truths—immutable necessary truths, forced on
human beings. The only way to account for there being such
necessary inescapable truths is their objective existence as truths in an
eternal mind. We serve and are closer to God in so far as we
contemplate eternal ideas in the mind of God. This, however, is not
all that is required; we also need a spiritual purification—goodness—
in order to approach God.
Aquinas
Thomas Aquinas (1225–74) was born of a noble family at Roccasecca,
Italy. From the age of five he began studying at the Benedictine abbey
of Monte Cassino. In 1239 he went on to the University of Naples,
where he studied the seven liberal arts of grammar, logic, rhetoric,
arithmetic, geometry, music, and astronomy; while at Naples he
entered the Dominican Order. His entry into this Order, with its
emphasis on poverty and evangelism, was opposed by his family to
such an extent that he felt the need to escape to Paris; but while on
the road to Paris, he was abducted by his elder brother and locked up
in the family castle at Monte San Giovanni. He was later held
prisoner in Roccasecca for over a year. His family was unable either
to strip him literally of his Dominican robes, or to persuade him to
renounce the Order. While he was imprisoned his brothers sent him a
seductress; but he drove her from the room with a burning brand,
and the event merely reinforced his commitment to chastity.
Eventually his family relented and he returned to the Dominican
Order, first at the University of Paris in 1248, then at Cologne under
Albert the Great. During this time he became deeply versed in the
works of Aristotle.
He returned to Paris in 1252 for advanced study, and he lectured
there in theology until 1259. The next ten years of his life were spent at
various Dominican monasteries near Rome; in 1268 he returned to
teach again at the University of Paris. In 1272 he went to teach at the
University of Naples; but ill-health forced him to stop work. In 1273 he
had a mystical vision which caused him to regard his intellectual work
as worthless—he consequently ceased work on the massive Summa
theologiae. In 1274 he was journeying to Lyon for a meeting of the
Aquinas 59
church council, but had to rest at Fossanova, not far from his place of
birth, owing to illness; there he died in 1274.
Aquinas’ character seems to have been one of imperturbability, and
there is no doubting his sharpness of intellect. After his death the
teaching of Aquinas and Thomism formed the official doctrine of the
Dominicans, and this was adopted by some other Orders, but it was in
general relatively neglected by the Catholic Church. However, in the
nineteenth century Aquinas was commended by Pope Pius IX as the
premier figure of Catholic philosophy and theology.
Aquinas’ thought owes a great deal to Aristotle, and he attempts to
reconcile the central tenets of Aristotelian philosophy with Christian
dogma; these attempts deal with issues like the nature of God, our
means to salvation, and our understanding of the nature of creation.
Aquinas’ thought begins with the presupposition that the universe is,
at least partly, intelligible to finite human intellects: the structures and
laws of the universe can be understood.
Aquinas hatches a compromise between the conclusions derived
from our natural cognitive faculties (the senses and reason of secular
philosophy), and conclusions derived from divine revelation (the faith
of divine theology). One could dismiss one or the other as worthless,
or say that each one ultimately depends on the other, as Augustine
does; Aquinas however maintains the distinction, and says that they
are two generally autonomous ways of looking at the same object,
namely God. Whereas our natural cognition works “from below” to
know God through His effects as the creator of the world, divine
revelation—supernatural cognition—works “from above” to know
God as cause. Thus faith (fides) and scientific knowledge (scientia) are
sharply distinguished not by object, but by method. Both are cognitive
processes involving the assent of the intellect to truths; but whereas
faith requires the addition of the will in order to believe truths with
certainty, scientific knowledge requires no such application of will
since the intellect either intuitively “sees” truths immediately, or
argues validly to establish truths from intuitively known premises.
Within theology we can make a distinction between supernatural
and natural theology: respectively, truths revealed about God and
other elements of Christian doctrine which depend on divine
revelation (grace, which derives from the Latin gratia, meaning
favour), and those that can be known through natural powers of
cognition. There is also an overlap of truths: some truths are both
revealed and known through being provable by natural cognition. In
this sense natural theology is part of supernatural theology. So the
totality of truths grasped by the human mind has three parts.
(A) That which is believed only in virtue of divine illumination or
revelation.
(B) That which is believed by divine revelation and is known by
being provable by natural cognition.
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(C) That which is known by natural cognition.
Ideally a conflict will never arise between the deliverances of the
revelations of faith, and the proofs of natural reason; but in the latter
we are fallible, and a conclusion derived from reasoning that conflicts
irreconcilably with a properly understood truth of faith shows that we
have made a mistake in our reasoning. But we have, ideally, a twofold
route to some Christian truths.
Natural cognition is made up of the senses and the intellect, and of
these the senses are primary both genetically and logically for
knowledge of existing things and for possession of abstract ideas; all
the materials of our intellectual faculty—our ideas—are abstracted
ultimately from the senses. The intellect is involved in forming
judgements about what we perceive: that what we perceive really
exists, that it has certain properties and that it is a certain kind of
thing. The intellect also engages in abstract reasoning. The senses see
X; the intellect actively judges X as X; the intellect goes on to
understand and think of X when it is not perceived. The intellect goes
beyond the sensory experience in forming a judgement, which is an
affirmation or denial of some truth; this goes beyond the mere fact of
one’s having a certain experience. The sensible aspects of particular
things (red, sweet, warm, etc.) are given through sense-perception
alone; but the intelligible aspects of particular things (that they exist,
that they actually have certain properties and are certain kinds of
things) are derived not from the passive association of the ideas of
senses alone, but in conjunction with an active synthesizing and
interpretative intellect, which forms from the ideas of sense complex
conceptions and hypotheses. The intellect forms concepts—universal
ideas—of things by abstracting general ideas from sense-experience;
the intellect thinks of the nature of those things and how they are
connected to other things by understanding those general concepts.
Aquinas follows Aristotle closely in not supposing that essences (the
“whatness” of things) can exist apart from individual things;
philosophically speaking, there is no universale ante rem, that is, essence
before or apart from individual things; rather, essence is universale in re,
present in individual things, in the sense that real things are real
substances and are always compounded of two elements.
(a) Essence (essentia, quidditas, natura). This is “whatness”; viewed
epistemologically through a definition it tells us what a thing is.
(b) Existence (esse, which is a form of the Latin verb “to be”; but esse
is also used as a noun). This is the fact that a thing is.
The difference between a mere essence (quidditas) and real substance is
existence (esse); existence is what turns, by being “added” to it, a
merely potential essence into an actual individual substance. This is
the primary move from potentiality to actuality: mere potential
Aquinas 61
existence to actual existence. Once a certain essence is actualized, there
is a further process of change from potential to actualization as the
essence brought into existence strives to fulfil its potential within its
kind; an acorn (an actual acorn, but potential tree) will grow into a tree
(an actual tree). The terms above in (a) and (b) roughly correlate with
the following.
(a’) potential (potentia, potency)
(b’) actuality (actus, act).
The difference between essence and potentiality is partly one of
generality; to speak of essence is to imply some determinate
potentiality: a certain “so-and-so”; whereas to speak of potentiality is
to suggest mere possibility: some “so-and-so” or other. Anything that
is not logically impossible has potentiality in the second sense.
To know the essence of something is to know its real definition, the
essential features without which a thing would cease to be the kind or
sort of thing it is. The accidental features that an individual kind of
thing has are those features which it can lose or gain while remaining
the same kind of thing. It is most important to note that Aquinas
thinks that in giving a definition of the essential nature of an
individual, he is giving a real definition; that is, the definitions are not
a function of the way we conceptually happen to divide up the world,
rather the definitions, if true, reflect accurately the way the world
divides itself up.
The distinction between essence and existence is also a real
distinction. That is not to say we ever encounter in the world pure
existence or pure essence, but the distinction is real in the sense of
being independent of human cognition; it is not a distinction projected
onto the world by the mind. For to say what something is is one thing,
but to say that it is, is another; we can know what a dog is—the essence
“dogness”—without committing ourselves to affirming either the
existence or non-existence of dogs. Another way of putting this is to
say that essences have no existential import. This is true for all entities
except God; He alone has existence as part of His essence. For all other
beings, existence (esse) is something added to essence—added to a
mere determinate potentiality—by God; thus all things depend
ultimately on God. Essence and existence are never found in
separation; nothing simply is, a thing always is a determinate kind of
thing; to be is to be a “so-and-so”; to be is always a determinate way of
being. The obvious limitation of individual substances is explained by
essences receiving esse and at the same time limiting that esse to a
certain way of being. In God the esse is unlimited, and also eternal;
there are no limits to God’s being; He has “fullness of being”.
For Aquinas as a Christian, unlike for Aristotle, the existence of
things cannot be taken for granted but requires explanation. Aristotle
thought that the world exists eternally, and that any change in the
62 Medieval philosophy
world is not a change from absolute non-existence (nothing) to
absolute existence or vice versa, but a change either of an accident, or
from one form of substantial being to another. For example a
substantial change occurs when a tree ceases to be a tree and becomes
ash when it is burnt. For Aquinas the very fact of existence itself is a
problem; given that nothing, except God, has existence as part of its
essence, an explanation beyond the essences of things is required to
explain why anything is at all; that explanation derives from God the
creator who adds esse to essences.
Apart from God, no essence is fully actualized. In God’s case, the
positive essence is fully actualized. God does not merely actualize His
divine essence; He actualizes it all the way, so to speak. If we take any
other entity, we will always have an entity which has potential within
its kind—its essence will not be fully actualized; there will be aspects
of its essence that it does not fully exemplify. God’s absolute perfection
is to be identified with His complete actualization of His positive
divine essence—He is pure act (actus purus); He contains no
unactualized potential of His positive divine essence.
The relation between essence and existence, and between potency
and actuality, applies to any substance whatsoever. It must not be
supposed that all real substances must be material or corporeal; not
only material things have esse. The analysis of material things
introduces another pair of terms,
(i) form (morphe)
(ii) matter (hyle).
This gives a hylemorphic theory of material substance. In the case of
material substances, potential corresponds to matter; the matter is
potentially a “so-and-so”, and is actualized as an individual separable
thing of a certain kind by taking on a certain form; that form is
actualized in that matter. However, pure matter (materia prima) would
be completely ineffable; it would by definition possess no character, no
whatness. Only by the addition of form in act in the matter does it
become a determinate “so-and-so”; matter as a mere determinable is
not possible, although we can understand what we mean when we talk
of it. The notion of pure potentiality as pure matter is impossible as
something that exists—it would indeed be a contradiction—but it is
intelligible conceptually. Indeed, pure potentiality cannot in any case
exist. The soul is the form of human beings; and souls are individuated
by the matter of the body of which they are the soul. But pure forms
can exist, as well as material substances, when certain non-material
essences receive esse. What Aquinas has in mind here seems to be a
three-level hierarchy of being.
(1) Corporeal substances. These are matter and form; they are
perishable and finite.
Aquinas 63
(2) Incorporeal limited substances. These are pure form—spiritual
entities, which although imperishable are finite. The kinds of
entities Aquinas has in mind here are the separated soul and
angels.
(3) Incorporeal unlimited substance. This is pure act; all aspects of
the positive essence receive existence (esse). This is, in fact, God
who alone exists necessarily, since in Him alone His way of being
must be conceived as including existence; in Him no distinction
can be made between the essence He has and His existence, for
He necessarily completely actualizes His essence, all the positive
aspects of the divine essence there are; there is nothing He is only
potentially; there is nothing divinely positive He is not.
The object of human knowledge in intellectual cognition is the
discovery of what essence is actualized in any individual. We
understand substances in so far as we come to know the essence that is
in act—is esse—in substances. Aquinas holds that for each known truth
there must always be something existing (esse) that corresponds to that
truth. Individual substances are understood by us not as individuals
qua individuals (individual things as such: features which constitute
their particularity), but through knowing that which is general or
common in them that defines the nature of the kind in which all the
individuals of a certain kind share. Thus we know a dog in so far as we
know the real definition of “dog”, and hence understand it in its
essential dogness; we do not know the dog in its full particularity
because the terms we apply always have some generality of
application.
An essence is what must be the case for a thing to be what it is: that
which a thing cannot lack and still be what it is. Thus understanding
what a thing is—its essence—is logically independent of the fact that a
thing is, its existence. I can understand what a dog or a Phoenix is
independently of whether it is. The essence of X is given in a set of
necessary and sufficient conditions a, b, c for X to be the kind of thing
it is. In this way we can form a real definition: X is of a specific kind if,
and only if, a, b, c are true of X. When we are correctly said to know X,
the aspect of X we know is that set of features X has in common with
all and only other Xs of the same kind. We would not understand a
clock as a clock by referring to its colour or the scratch on the face, but
in so far as we understand that in virtue of which a clock is a clock:
what makes it distinctively a clock and not another kind of thing. We
understand the nature of the clock by understanding those common
features shared by all and only clocks which define them as clocks.
Then what makes a clock or a dog a particular clock or dog cannot be
its essence or form, since that is common to all instances of the same
kind, but must, Aquinas argues, be its being formed of a quantitatively
or numerically different parcel of matter.
64 Medieval philosophy
With incorporeal or spiritual substances such a method of
individuation is clearly inapplicable; he suggests that each incorporeal
substance must be individuated by essence; that is, the essence of each
soul or angel must be different, so each angel differs in essence as a
dog does from a cat; each angel is of a different, and unique, kind.
Aquinas strikes a middle course on the question of the reality of
universals. Universals are general concepts or categories with which
we talk about the world and with which we classify particulars into
kinds or sorts. Aquinas adopts a form of moderate realism. He rejects
the full realism of Plato, whereby universals exist as real entities in a
world of intelligible Forms independently of the world of sensible
things. He also rejects conventionalism, whereby universal concepts
are mere arbitrary, subjective mental constructs, for which the most
that can perhaps be said is that they are made for our convenience.
Aquinas compromises: universals are objective in being real,
extramental and immutable, but they exist in instances of individual
kinds of things and cannot exist apart from those instances. Universals
or kinds as such exist only in virtue of there being individual actual
instances of those kinds. Only individuals exist, but the natures of
those individuals radically resemble each other and are understood
from this essential common resembling nature as being members of
universal classes or species—for example, humanity, dogness, justice.
Individual material things of the same kind are the same kind in virtue
of sharing a substantial form; but that substantial form, although it
cannot exist apart from the individuals who share it, is nevertheless
something objective in the world, and derives its objectivity from the
really existing common nature shared by individuals of the same class.
The world divides itself into kinds, so to speak; the kinds are real and
there to be discovered, and are independent of our subjective mental
classifications. Abstracted forms are derived from individual instances;
the logical rules of the combination of such forms are revealed in real
definitions; the forms, through real definitions, give concepts which
have fixed immutable objective meaning; the forms and their logical
combination, known through their concepts, are the proper objects of
knowledge. Knowledge of the forms, through real definitions, is
derived from sensory experience and the intellectual faculty of
abstracting general concepts from the resembling essential nature of
instances of individuals of the same sort. Thus although universals do
not exist as separate entities, they are objective in reflecting the
extramental common defining real natures of individuals.
Ockham
William of Ockham (c.1285–1349) was born in the village of Ockham
outside Guildford near London. The details of his life are obscure, and
Ockham 65
often a matter of conjecture. Of his early life nothing definite is known.
We know that he was ordained subdeacon in 1306. He became a
student at the University of Oxford around 1309 and soon a member of
the Franciscan Order. He pursued his studies at Oxford until 1315;
from 1315 to 1317 he gave lectures on the Bible and, from 1317 to 1319,
lectures on the hugely influential Four books of sentences by Peter
Lombard. The Four books of sentences was compiled around 1150; it
brought together the teachings of the early Church Fathers—especially
St Augustine—and it was a cornerstone of Christian theology.
Ockham completed the requirements for the degree of Magister
theologiae, but he never became a Master occupying the Chair of
Theology. This was probably due to the opposition of Lutterell, a keen
Thomist, to the appointment of Ockham; Lutterell had been removed
from the post of Chancellor of the University by 1322. Lutterell left in
1323 for Avignon, the residence of Pope John XXII; there he set about
blackening Ockham’s name by accusing him of holding in his
Commentary on the Sentences heretical and dangerous views. Ockham
was summoned to Avignon in 1324 to have his views examined; the
examination lasted for three years. Ockham refused to retract his
views.
Michael of Cesena, the General of the Franciscan Order, also faced
the condemnation of the Pope for his Order’s espousal of absolute
apostolic poverty. Ockham joined forces with Michael, his superior,
and, together with another Franciscan, Bonogratia, they fled from
Avignon in 1328, seeking the protection of the German Emperor, Louis
of Bavaria. Louis had installed in Rome an antipope who had in return
crowned him head of the Roman Empire. Ockham, Michael and
Bonogratia joined the new Emperor in Munich, and were
excommunicated from the Catholic Church and their own Order. In
1342 Michael died; in 1347 Louis also died. This left Ockham in an
extremely vulnerable position; he sought reconciliation with the
Church and his Order. Before any reconciliation could be decided
upon, Ockham died in 1349, probably of the prevalent Black Death. He
was buried in the old Franciscan church in Munich; but in 1802 his
remains were moved to a place that is still unknown.
Ockham may be seen as something of a philosophical Janus, since
like that god, his philosophy looks in two opposite directions; it looks
back to the Middle Ages, and it looks forward to some of the ideas of
the Enlightenment—to the empiricism of John Locke (1632–1704) and
David Hume (1711–76), and aspects of materialism—but the forwardlooking
characteristics must not be overemphasized; Ockham would
have seen himself not as a philosophical revolutionary, but merely as
reinterpreting an already established tradition. The chief problem was
still to reconcile Aristotle and Christianity. A sharp distinction is found
in Ockham’s thought between reason and faith. The truths of theology
are based on revelation and are a matter of faith, and they are neither
66 Medieval philosophy
provable nor refutable by any process of natural cognition in secular
philosophy. Theology retreats to a domain of truths about which
natural reason can have nothing to say.
The chief characteristic of the tradition to which Ockham was heir
was realism in its various forms: that the human intellect can discover,
in the particular things perceived by sense-experience, a real objective
system of universal common essences which become somehow
individualized, and which can either have an independent existence
from, or exist as a real part of, particular individuals. These essences
have an extralinguistic reality over and above—really distinct from—
the particular features of individuals which are classified in virtue of
the essence as being the same kind. Then from the linguistic
connections in meaning between the terms that refer to these real
essences we can know necessary truths about an extralinguistic reality.
Necessary truths can be known about the world we perceive and about
God. The universals we intellectually abstract—humanity or horse—
from particular individuals are not merely arbitrary subjective mental
or linguistic constructs, or merely derived from objective particular
features of individual things, but have a real ontologically distinct
reference in or beyond the world, independent of individuals, or their
particular features, whereby such individuals fall into the general class
designated by universal terms. In short, the linguistic distinction we
make between universal and particular terms has a real ontological
counterpart.
The problem of universals—what if anything universal terms stand
for—to which realism is one answer, centres on the problem of the
relationship between the universality of concepts and our apparently
encountering as independent objects only particulars. Realists would
argue that, without a suitable system of real entities for universal terms
to refer to, our system of universal terms will be entirely arbitrary,
conventional and subjective. This would make any science, which will
inevitably be couched in general or universal terms (such as “body”,
“animal”, “heavy”), an arbitrary mental construction among other
possible constructions with no objective validity derived from its
reflecting an extramental reality; this leaves open the rationally
anarchic possibility of a variety of different incommensurable
conceptual systems of scientific explanation between which we can
have no common grounds or independent standard for a rational
choice.
Moderate medieval realism does not go all the way with Platonism,
which suggests that universal essences or “whatness”—such as
humanity, horseness, justice—can exist as Forms quite independently
of all particular individuals which are grouped together in virtue of
those universal essences. Moderate realism follows Aristotle in
maintaining that in some way there is a real distinction in the world
between the common universal essence and the individuating
Ockham 67
characteristics of particular things sharing that essence. Moderate
realism holds that, although the common universal essences of
individuals and those individuals cannot be found existing in
separation, the distinction between universal essences and particular
individuals which can be made in thought nevertheless reflects a real
distinction in things in the world. The same common nature or essence
is really distinct from things in respect of what makes them particular,
as it exists in all the particulars of the same sort, and it is this that
makes them the kind of things they are.
The forward-looking aspect of Ockham’s philosophy resides in his
rejection of realism and his alternative explanation: his rejection of the
reality of a world of intelligible, literally common, essences or forms
ontologically or really distinct from the characteristics that pick out
individuals, and his consequent propagation of nominalism and
empiricism. His nominalism and empiricism are closely linked.
Ockham objects to the idea of some literally common nature shared
by all and only individuals of the same kind; if this common nature is
singular and indivisible, then it cannot be shared by many individuals,
and if the common nature is many, then each instance of the many
must be singular and itself individual and cannot be shared in
common between various individuals.
Ockham does not deny that the world falls into a mind-independent
system of natural kinds—in this sense he is still a realist. What he
denies in his nominalism is that a condition for its being correct to talk
about a natural order of kinds of individual things is the positing of
common natures or essences, ontologically or really distinct from the
individualizing characteristics, and shared by all and only the
individual things of the same kind. Moreover, he thinks that such a
view is an unnecessary misinterpretation of Aristotle. He denies in this
nominalism that universals subsist as ideas in the mind of God prior to
their actualization (their receiving esse); God is not necessitated even to
this extent; He is not constrained to create, if He creates at all, a
particular world-system of kinds. There is, therefore, no system of
essences whose necessary relations could be known a priori.
For Ockham, universality is a property primarily of thoughts,
secondarily of language which expresses thoughts, and not of entities
or natures distinct from the individual characteristics of things in the
world. Universality is the property of a thought, a generalized
abstractive cognition, which is entertained in such a way as to be
equally truly predicable of, or usable of, more than one individual.
Thus the term “city” is used of London, Paris, New York. Ockham’s
view is roughly equivalent to saying that universals are concepts,
along with the commitment that the being of the concepts is as mental
states. Nominalism holds that the only thing strictly in common
between individuals falling under a universal name is that they all fall
under that name.
68 Medieval philosophy
The question arises as to why we apply the same universal name to
many individuals. Ockham’s empiricism complements his nominalism
by maintaining that there are no literally common real essences
graspable by the intellect, but only individuals apprehended by the
senses between which we perceive similarities in the individuating
characteristics, and it is from these albeit objective but nevertheless
contingent similarities that we derive the meanings of universal terms
and their range of application to a determinate class of individuals.
Thus the connotation or meaning of a universal term such as
“humanity” is whatever characteristics we perceive as similar between
all those individuals whereby we classify them as human. This list of
characteristics defines “humanity” and gives us criteria for deciding
whether any given individual should be included under that heading;
the denotation or reference of the term “humanity” is then just all
individual human beings. The meaning of a universal term such as
“humanity” is not explained by its denoting a common essence distinct
from the characteristics of particular human beings; its meaning is
explained by the similar characteristics of a number of individual men,
in virtue of which we call them all “men”. Talk of something “similar”
between many individuals may seem to evoke a common nature again;
but Ockham would say that we perceive similarity not by perceiving
some literally identical common nature distinct from the individuating
characteristics, but in virtue of a resemblance between the
characteristics which are part of the natures or features of the
individuals themselves.
Thus Ockham denies that there is a metaphysical problem of
determining in virtue of what universals are individualized, since
there are no such universals to be individuated. Aquinas had
suggested that universals are individuated in virtue of their being
exemplified in a different parcel of stuff or matter; Duns Scotus (c.
1266–1308) rejected this and suggested that beside universal essences—
what features a thing cannot lack and still be the kind of thing it is—
there is an individuating essence, the haecceitas or individualizing
“thisness” of a kind, which gives this horse. Ockham, however, has the
logical problem of showing how to reduce universal concepts to terms
that signify what he regards as the only existents, individuals; and he
has the epistemological problem of saying how from experiencing only
individuals we form universal concepts.
It should be pointed out that for Ockham the primary carriers of
meanings are mental expressions—states of mind—with which written
and spoken expressions become associated by convention. Mental
signs mean what they stand for directly; linguistic expressions are
signs only conventionally; thus the mental sign for rain is the same for
the speaker of any language, but its linguistic expression may be
different.
Terms are elements in propositions and they take on different
Ockham 69
functions depending on the proposition they are in; in particular they
acquire a determinate “standing for” (suppositio) function. Here we are
talking of natural terms or concepts, not the conventional terms of any
particular language; the terms “homme” and “man” are conventional
terms for the same natural sign or concept. Ockham distinguishes
between “terms of the first intention” and “terms of the second
intention”. For example, a singular term such as “Socrates” stands as a
natural sign for the thing Socrates and is of the “first intention”. A
universal term such as “species” is of the “second intention” and
stands not immediately for things that are not themselves signs, but
for other signs that do stand immediately as signs for things. Thus,
“Socrates” is a sign for the individual man Socrates; “species” stands
not immediately for individual things, but for terms of the “first
intention” such as “man”, “horse” and “dog”; the term “species” can
be predicated of the terms “man”, “horse” and “dog”, each of which
stands for all the members of a different class of individuals, and says
of these terms that they are all species-terms which are the names of
many things. Ockham contends that the realist belief in universal
terms standing, albeit obliquely or indirectly, for entities distinct from
individual entities is a consequence of confusing the two levels of
intentions: terms that stand for things, and terms that stand for terms;
that is, talk about things in an object language, and talk about the
object language in a metalanguage. If we confuse these two we are
tempted to suppose mistakenly that metalinguistic talk is about things.
Nominalism is in accord with the most famous feature of Ockham’s
thought, “Ockham’s razor”; this is a methodological principle
designed to keep the number of kinds of entities posited as distinct in
the world to a minimum—it is a principle of parsimony. Ockham’s
objection to realism and the positing of real ontologically distinct
essences is partly just that they are unnecessary to explain how we
come to classify things in a universal manner. Logically what this
means is that apparent reference to real abstract entities by universal
terms can in principle always be replaced by an analysis of universal
terms, so that they refer only to individuals. Thus “man” signifies
merely the total disjunction: Socrates, or Plato, or Aquinas, and so on.
Relational terms such as “taller” do not denote entities distinct from
the individuals to which they apply; in referring to A being taller than
B, we are referring to only two entities, and the truth “A is taller than
B’’ is reduced to a truth about A (A is six feet tall) and a truth about B
(B is five feet tall). The only sorts of thing that exist are individuals:
individual substances and their individual qualities.
It has been objected that Ockham’s criticism of the real distinction
between essences and individuals misses the point, for he attacks a
position which the most important medieval thinkers such as Aquinas
and Duns Scotus never sought to defend. The accusation is that
Ockham thought that if the distinction between the common essence of
70 Medieval philosophy
individuals and what constitutes their individuality were to be a real
distinction, then it must be a distinction between things of the same
sort, such as exists between any two existing individuals, and that
Ockham was led to this assumption by thinking of the attribution of
essences as noun-like rather than verb-like. If we think of the
attribution of essences or forms as more verb-like than noun-like—as
in “humanizing”, “equinizing”—we will see that there is a formal
objective extralinguistic distinction being made which is separable in
thought and is nevertheless not a distinction between separable
individual entities. It is not clear whether this pointing up of the
distinction between the grammatically verb-like use of ascribed
essences to things, as opposed to naming those same things, is
sufficient to maintain that there is a corresponding metaphysical
extralinguistic distinction between the common natures and the
particular features of individuals.
Moving to Ockham’s epistemology, we find that he distinguishes
between intellectual acts of apprehension and judgement:
apprehension or cognition is awareness on the basis of which a
judgement can be made, which is an intellectual assent to the truth or
falsity of a proposition. He further contrasts an intuitive cognition, on
the basis of which one is in a position to make a judgement of
contingent fact which is evident, and an abstract cognition, on the basis
of which we are not in a position to make an evident judgement of
contingent fact—such contingent judgement will concern whether an
object exists or whether it has some contingent property. The objects of
these cognitions are the same; what differs is the manner in which they
are apprehended; in an intuitive cognition the apprehension of the
object is caused immediately by the object apprehended; in an abstract
cognition the apprehension of the object is not caused immediately by
the object apprehended, but it always presupposes an intuitive
cognition of the object at some previous time. From an intuitive
cognition of X, or X as f, we can judge evidently that it is true that X
exists, or that X is f. Once we have an intuitive cognition of X, or X as f,
it can be stored in the memory as an acquired capacity (habitus) so we
can then form an abstract cognition of X, or X as f, which is divorced
from X existing or not existing, or X actually being f or not being f; but
this abstract cognition of X, or X as f, does not put us in the position to
make the judgement we might make concerning X evident. If I saw you
sitting in my study, I would be in a position to form an evident
judgement that it is true that you are sitting in my study; if, however, I
did not see you, but nevertheless formed from an abstractive cognition
the judgement that you were sitting in my study, then the judgement,
although it may be true, may also be false, and is not in any case
evident. Ockham is realist with respect to individual objects and their
individual properties in the external world: he does not doubt that in
mental acts of intuitive cognition what we directly apprehend is
Ockham 71
constituted by objects and their properties just as they really are in the
external world outside the mind. In intuitive cognition there is no
distinction between the way things seem to us and the way they really
are; the way they seem is how they are. Ockham holds that we can also
have intuitive cognition of introspectively apprehended mental states.
In the natural course of events, if we have an intuitive cognition of
X, then X exists, since X is a part of the cause of the cognition of X;
thus the judgement that X exists is evident. However, since it is
logically possible, God could produce supernaturally in us the same
mental state as a cognitive intuition—that is, phenomenologically the
same intuition, which is as if we were having a real intuitive
cognition—without the object existing, which would in natural
circumstances suffice for the evident judgement that the object exists.
But, in fact, God does not normally act like this, although He did so in
the case of the prophets.
Ockham’s empiricism surfaces in his account of explanations of the
natural world. Strictly speaking, science is concerned with necessary
universal truths concerning that which must be and cannot be
otherwise, expressed in propositions that are proved from self-evident
propositions by syllogistic deductive reasoning. But one needs
experience even to understand the meaning of the terms in
propositions—at least those that stand for things—even when, once
understood, they are self-evident propositions; for to understand the
meaning of the terms we need a primary experience of what the terms
stand for. For Ockham, as for Locke, there are no innate ideas which
could account for this; all our ideas, by association with which words
get their meaning, are derived from experience.
Science in a narrow sense includes only necessary provable
propositions; and since the existence and nature of the world are in all
ways contingent (that which may be true or may be false), it would
seem that a science of the world is not strictly possible. In
mathematics, geometry, metaphysics and theology, there are truths
which are quite independent of whether any world exists or not and
these are suitable subjects for scientific knowledge. However, Ockham
extends science (scientia) to include hypothetical or conditional
premises of demonstrations or proofs, and evident contingent
judgements made on the basis of intuitive cognitions.
Ockham maintains that God must be supremely unnecessitated,
being completely free and completely omnipotent. This leads him to
assert that the world is radically contingent in its existence and nature;
necessity applies only within thought and language, not to events or
things in the world. All that is not self-contradictory is possible; what
is actual but not necessary cannot be determined by a priori reason or
logic alone; reason and logic can determine only what is necessary,
impossible and possible, not what is actual and contingent among
what is possible. Logically speaking in the world anything could
72 Medieval philosophy
follow from anything else, and the only way to determine what things
there are, and how things are connected, is by experience. Ockham
does not deny that there are real objective causal connections in
nature; the order we appear to see is not merely derived from the
conventional use of expressions; he does not deny that there is a
natural order in the world that can form the basis for the discovery of
universal connections which are the aim of science; what he denies is
that these universal connections in fact have any metaphysical
necessity which could be discovered through deductive reasoning
alone. All those connections between things and events that are not
merely analytically true by the definitions which give identifying
criteria are radically contingent and can be known to hold only from
intuitive cognitions. Thus to have new knowledge of connections
which goes beyond what is already assumed in definitions, as is the
case with causal connections, we rely on experience. If all connections
between things and events were analytic and merely followed from
definitions, then working them out would be a purely linguistic
matter. Clearly we suppose that most connections are not definitional
in this way, in which case the connections can be known to hold only
by experience.
Ockham does not tackle the question which was to concern Hume
much later, in the eighteenth century, of how we can rationally justify
the belief that there is any objective natural system of laws at all—the
problem of the “uniformity of nature”—or how the evidence from the
experience of a finite number of singular instances can ever justify the
assertion of universal laws of the form “All As are Bs” or causal
connections of the form “If A occurs, then B must occur”. Ockham
thinks that God has, as a matter of fact, so arranged things that we can
discover objective regular natural laws; but these laws are only
contingently—in fact—true, and God could have arranged the laws
quite differently; He was not bound by any kind of necessity to
arrange things the way He actually arranged them. It follows that if
the arrangement of things is not a matter of necessity, the discovery of
the arranged regularities is not knowable by a priori deductive
reasoning alone, which can give us knowledge only of necessities (that
which must be), impossibilities (that which cannot be) and possibilities
(that which may or may not be); rather, we require experience in order
to discover what actual contingent (that which is, but need not be)
arrangement exists. God maintains the natural order so that we can
rely (barring miracles) on B always following A; A is a sign that B will
follow, and we can be confident, thanks to God, that B will follow. This
is not to say that God, and not A, is the real cause of B, but merely that
God chooses to maintain a natural order whereby, albeit contingently,
A causes B.
Ockham 73
continued to ...