extreme were called Epicureans, and whom Dante found in hell. In fact, Aristotle's doctrine is
complex, and easily lends itself to misunderstandings. In his book On the Soul, he regards the soul
as bound up with the body, and ridicules the Pythagorean doctrine of transmigration (407b). The
soul, it seems, perishes with the body: "it indubitably follows that the soul is inseparable from its
body" (413a); but he immediately adds: "or at any rate certain parts of it are." Body and soul are
related as matter and form: "the soul must be a substance in the sense of the form of a material
body having life potentially within it. But substance is actuality, and thus soul is the actuality of a
body as above characterized" (412a). Soul "is substance in the sense which corresponds to the
definitive formula of a thing's essence. That means that it is the 'essential whatness' of a body of
the character just assigned" (i.e. having life) (412b). "The soul is the first grade of actuality of a
natural body having life potentially in it. The body so described is a body which is organized
(412a). To ask whether soul and body are one is as meaningless as to ask whether the wax and the
shape given it by the stamp are one (412b). Self-nutrition is the only psychic power possessed by
plants (413a). The soul is the final cause of the body (414a).
In this book, he distinguishes between "soul" and "mind," making mind higher than soul, and less
bound to the body. After speaking of the relation of soul and body, he says: "The case of mind is
different; it seems to be an independent substance implanted within the soul and to be incapable of
being destroyed" (408b). Again: "We have no evidence as yet about mind or the power to think; it
seems to be a widely different kind of soul, differing as what is eternal from what is perishable; it
alone is capable of existence in isolation from all other psychic powers. All the other parts of soul,
it is evident from what we have said, are, in spite of certain statements to the contrary, incapable
of separate existence" (413b). The mind is the part of us that understands mathematics and
philosophy; its objects are timeless, and therefore it is regarded as itself timeless. The soul is what
moves the body and perceives sensible objects; it is characterized by self-nutrition, sensation,
thinking, and motivity (413b); but the mind has the higher function of thinking, which has no
relation to the body or to the senses. Hence the mind can be immortal, though the rest of the soul
cannot.