[ Pobierz całość w formacie PDF ]
knowledge; article three rejects the theory of innate ideas, and article
four returns to the criticism of Plato s theory of Ideas.
The crudest form of the materialist theory of knowledge was that
developed by some of the Presocratic philosophers on the basis of
90 Aquinas on Mind
the slogan that like knows like. In order to know what is material,
our minds must share the nature of matter.
The earliest physicists, starting from the premise that the things
known by the soul are corporeal and material, maintained that
they must exist in a material way in the knowing soul as well. So
in order to allow the soul knowledge of everything, they
postulated that it had a nature in common with everything.
Because the nature of compounds is determined by their elements,
they attributed to the soul the nature of whatever they regarded
as elemental: thus, if a philosopher thought that fire was the
universal element, he would say that the soul was made of fire;
and similarly with air and water.
(S 1, 84, 2c)1
In the second article, Aquinas takes a stand against the materialists
who argued that if the soul was to know matter it must contain
matter, since like can only be known by like. In reply, he draws out
into patent nonsense the nonsense that is latent in the materialist
position.
If it was necessary, he says, for a thing known to be in the soul
materially, then there would be no reason why things which exist
materially outside the soul should lack knowledge. Let us suppose
that the materialist was right, and it was the presence of actual fire
in the soul that explained how the soul could know fire. In that case,
why should not fire outside the soul also be conscious of fire?
Modern materialists identify the mind with the brain. They then
identify the problem of explaining how the mind knows X with the
problem of explaining how X is in the brain not literally, but in
encoded form. Once they have shown that there is an encoding of X
in the brain (or, more plausibly, once they have shown that, for all
we know, there may be an encoding of X in the brain), they think
that they have explained knowledge of X. But in fact the problem
remains just where it was: for the problem of knowledge is the
problem of what makes a pattern into a code.
Aquinas would say: let us suppose that X itself is present in the
brain, and not just in coded form. How does that explain knowledge of
X? After all, there is in the brain oxygen itself, and not merely a code
for oxygen. But the presence of oxygen in the brain does not explain
how a scientist knows what oxygen is. There is oxygen in the brain of
many mammals who have not the faintest idea what oxygen is. And if
Sense, imagination and intellect 91
the presence of oxygen explained knowledge of oxygen, then, as
Aquinas would say, fire would know what oxygen was.
The account of innate ideas in article three is much less carefully
worked out than that in the Prima Secundae in the treatment of
dispositions, in the first article of question fifty-one. The position
which Aquinas takes in the debate about the existence of innate ideas
is a balanced one, taking acount of arguments on both sides of the
question. There are, he says, no completely innnate dispositions to
activity which are present in all members of the human race; but some
men, because of the fortunate constitution of their bodies, are born
with gifts of intelligence or advantages of temperament which are
denied to other men; and these natural endowments are dispositions of
a kind (S 1 2, 51, 1). Again, there are no completely innate ideas or
beliefs; but belief in self-evident propositions is innate in a specially
qualified sense. Because of the nature of his spiritual soul , St Thomas
tells us, a human being, once he knows what a whole is and what a
partis, knows that every whole is greater than any of its parts. But, he
continues, a man cannot know what a whole is or what a part is except
through the possession of concepts derived through the senses. The
understanding of self-evident principles is thus in one sense innate and
in another sense acquired by experience (S 1 2, 51, 1).
Plato had maintained, Aquinas says, that the human intellect
naturally contained all intelligible ideas, but was prevented from using
them because of its union with the body. Against this Aquinas
marshals both empirical and metaphysical arguments.
If the soul has a natural knowledge of all these things it does not
seem possible that it should so far forget this natural knowledge
as to be ignorant that it has it at all. For nobody forgets what he
naturally knows, as that the whole is greater than its parts and
so on. Plato s theory seems especially unacceptable if the soul is,
as maintained above, naturally united to the body; for it is
unacceptable that the natural operation of a thing should be
altogether impeded by something else which is also natural to it.
Secondly, the falsity of this theory appears obvious from the fact
that when a certain sense is lacking, there is lacking also the
scientific knowledge of things perceived by that sense. A blind
man, for instance, cannot have any knowledge of colours. This
would not be the case if the soul s intellect were naturally
endowed with the concepts of all intelligible objects.
(S 1, 84, 3)2
92 Aquinas on Mind
Later, Aquinas praises Aristotle for taking a middle course between
the innate idealism of Plato and the crude empiricism of
Democritus.
Aristotle maintained that the intellect had an activity in which
the body had no share. Now nothing corporeal can cause an
impression on an incorporeal thing, and so, according to
Aristotle, the mere stimulus of sensible bodies is not sufficient to
cause intellectual activity. Something nobler and higher is needed,
which he called the agent intellect: it makes the phantasms
received from the senses to be actually intelligible by means of a
certain abstraction.
(S 1, 84, 6)3
Aquinas contrasts the abstraction made by the intellect with that
made by the senses. For even the senses, he explains, do abstract
in a way.
A sense-perceptible form is not in the same manner in the thing
outside the soul as it is in the sense-faculty. The sense-faculty
receives the forms of sense-perceptible things without their
matter, as it receives the colour of gold without the gold; and
similarly the intellect receives the ideas of bodies, which are
material and changeable, in an immaterial and unchangeable
fashion of its own.
(S 1, 84, 1)4
The less materially a faculty possesses the form of the object it knows,
Aquinas explains, the more perfectly it knows; thus the intellect,
which abstracts the ideas not only from matter but also from material
individuating characteristics, is a more perfect cognitive power than
the senses, which receive the form of what they know without matter
but not without material conditions (1, 84, 2). Perceptible qualities
outside the soul are already actually perceptible; but since there are
no Platonic Ideas, there is nothing outside the soul actually intelligible
corresponding to material objects.
Having rejected Platonic views of the origin of ideas, whether in
the pagan form that they derived from self-subsistent forms (S 1,
84, 4) or in the Christian form that they derived from knowledge of
the ideas in the mind of God (S 1, 84, 5), Aquinas presents as his
own the Aristotelian via media between empiricism and Platonism.
Sense, imagination and intellect 93
Aristotle took the middle course. He agreed with Plato that the
intellect differed from the senses; but he did not accept that the
senses had any activity of their own without the participation of
[ Pobierz całość w formacie PDF ]