Aristotle on the Soul
Matter and Form
Aristotle uses his familiar matter/form distinction to answer the question
What is soul? At the beginning of De Anima II.1,
he says that there are three sorts of substance:
The compound of matter and form
Aristotle is interested in compounds that are alive. These -
plants and animals - are the things that have souls. Their souls
are what make them living things.
Since form is what makes matter a this, the soul is the form
of a living thing. (Not its shape, but its actuality, that in virtue
of which it is the kind of living thing that it is.)
Grades of Actuality and Potentiality
Aristotle distinguishes between two levels of actuality (entelecheia).
At 412a11 he gives knowing and attending as examples of these
two kinds of actuality. (It has become traditional to call these first
and second actuality, respectively.) At 412a22-26 he elaborates this
example and adds this one: being asleep vs. being awake. But
he does not fully clarify this important distinction until II.5 (417a22-30),
to which we now turn.
At 417a20, Aristotle says that there are different types of both potentiality
and actuality. His example concerns different ways in which someone might be
described as a knower. One might be called a knower in the sense that
he or she:
A knower in sense (a) is someone with a mere potential to know something, but
no actual knowledge. (Not everything has this potential, of course. E.g.,
a rock or an earthworm has no such potential.) A knower in sense (b) has
some actual knowledge (for example, she may know that it is ungrammatical to
say with John and I), even though she is not actually thinking
about it right now. A knower in sense (c) is actually exercising her knowledge
(for example, she thinks thats ungrammatical when she hears
someone say with John and I).
- is a human being.
- has grammatical knowledge.
- is attending to something.
Note that (b) involves both actuality and potentiality. The knower in
sense (b) actually knows something, but that actual knowledge is itself
just a potentiality to think certain thoughts or perform certain actions.
So we can describe our three knowers this way:
- First potentiality
- Second potentiality = first actuality
- Second actuality
Here is another example (not Aristotles) that might help clarify the
A child (unlike a rock or an earthworm) can (learn to) speak French. A
Frenchman (unlike a Frech infant, and unlike most Americans) can actually
speak French, even though he is silent at the moment. Someone who is
actually speaking French is, of course, the paradigm case of a French
First potentiality: a child who does not speak French.
Second potentiality (first actuality): a (silent) adult who speaks French.
Second actuality: an adult speaking (or actively understanding) French.
Aristotle uses the notion of first actuality in his definition of the soul
The soul is the first actuality of a natural body that is potentially alive.
Remember that first actuality is a kind of potentiality -a capacity
to engage in the activity which is the corresponding second actuality.
So soul is a capacity - but a capacity to do what?
A living things soul is its capacity to engage in the activities that are
characteristic of living things of its natural kind. What are those activities?
Some are listed in DA II.1; others in DA II.2:
Movement and rest (in respect of place)
So anything that nourishes itself, that grows, decays, moves about (on its
own, not just when moved by something else), perceives, or thinks is
alive. And the capacities of a thing in virtue of which it does these
things constitute its soul. The soul is what is causally responsible
for the animate behavior (the life activities) of a living thing.
Degrees of soul
There is a nested hierarchy of soul functions or activities (413a23).
Growth, nutrition, (reproduction)
Intellect (= thought)
This gives us three corresponding degrees of soul:
Nutritive soul (plants)
Sensitive soul (all animals)
Rational soul (human beings)
These are nested in the sense that anything that has a higher degree
of soul also has all of the lower degrees. All living things grow, nourish
themselves, and reproduce. Animals not only do that, but move and perceive.
Humans do all of the above and reason, as well. (There are further subdivisions
within the various levels, which we will ignore.)
Soul and Body
A key question for the ancient Greeks (as it still is for many people today)
is whether the soul can exist independently of the body. (Anyone who believes
in personal immortality is committed to the independent existence of the soul.)
Plato (as we know from the Phaedo) certainly thought that the soul could
exist separately. Here is what Aristotle has to say on this topic:
. . . the soul does not exist without a body and yet is not itself
a kind of body. For it is not a body, but something which belongs to a body, and
for this reason exists in a body, and in a body of such-and-such a kind
So on Aristotles account, although the soul is not a material object, it is
not separable from the body. (When it comes to the intellect, however, Aristotle
waffles. See DA III.4)
Aristotles picture is not Cartesian:
There is no inner/outer contrast. The soul is not an inner spectator, in
direct contact only with its own perceptions and other psychic states, having
to infer the existence of a body and an external world.
There is thus no notion of the privacy of experience, the incorrigibility
of the mental, etc., in Aristotles picture.
The soul is not an independently existing substance. It is linked to the
body more directly: it is the form of the body, not a separate substance
inside another substance (a body) of a different kind. It is a
capacity, not the thing that has the capacity.
It is thus not a separable soul. (It is, at most, pure thought, devoid
of personality, that is separable from the body on Aristotles account.)
Soul has little to do with personal identity and individuality. There is
no reason to think that one (human) soul is in any important respect different
from any other (human) soul. The form of one human being is the same as the
form of any other.
There is, in this sense, only soul, and not souls. You and I have
different souls because we are different people. But we are different human
beings because we are different compounds of form and matter. That is, different
bodies both animated by the same set of capacities, by the same (kind of)
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lecture on Matter, Form, and Substance.
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Copyright © 2004, S. Marc Cohen