On The Soul
affection, then if mind is simple and impassible and has nothing in
common with anything else, as Anaxagoras says, how can it come to
think at all? For interaction between two factors is held to require a
precedent community of nature between the factors. Again it might be
asked, is mind a possible object of thought to itself? For if mind
is thinkable per se and what is thinkable is in kind one and the same,
then either (a) mind will belong to everything, or (b) mind will
contain some element common to it with all other realities which makes
them all thinkable.
(1) Have not we already disposed of the difficulty about interaction
involving a common element, when we said that mind is in a sense
potentially whatever is thinkable, though actually it is nothing until
it has thought? What it thinks must be in it just as characters may be
said to be on a writingtablet on which as yet nothing actually
stands written: this is exactly what happens with mind.
(Mind is itself thinkable in exactly the same way as its objects
are. For (a) in the case of objects which involve no matter, what
thinks and what is thought are identical; for speculative knowledge
and its object are identical. (Why mind is not always thinking we must
consider later.) (b) In the case of those which contain matter each of
the objects of thought is only potentially present. It follows that
while they will not have mind in them (for mind is a potentiality of
them only in so far as they are capable of being disengaged from
matter) mind may yet be thinkable.
Since in every class of things, as in nature as a whole, we find two
factors involved, (1) a matter which is potentially all the
particulars included in the class, (2) a cause which is productive
in the sense that it makes them all (the latter standing to the
former, as e.g. an art to its material), these distinct elements
must likewise be found within the soul.