summa-contra-gentiles

has a determinate bodily organ.
CHAPTER LXVIII 171
Therefore the imagination
is not the same as the possible intellect.
Hence it is said (Job xxxv. 11)
: Who teacheth us more
than the beasts of the earth, and instructeth us more than
the foivls of the air. Whereby we are given to understand
that man has a cognitive power above sense and imagination,
which are in other animals.
CHAPTER LXVni
HOW AN INTELLECTUAL SUBSTANCE CAN BE THE FORM OF
THE BODY
Accordingly from the foregoing arguments we are able to
conclude that an intellectual substance can be united to the
body as its form. For if an intellectual substance is not
united to the body merely as its mover, as Plato stated, nor
is in contact with it
merely by the phantasms, as Averroes
held, but as its form ;
and if the intellect whereby man
understands is not a preparedness in human nature, as
Alexander maintained, nor the temperament, as Galen said,
nor harmony, according to Emf)edocles, nor a body, nor
the senses or imagination, as the ancients asserted, it
follows that the human soul is an intellectual substance
united to the body as its form. This can be made evident
as follows.
For one thing to be another's substantial form, two
conditions are required. One of them is that the form be
the principle of substantial being to the thing of which it is
the form : and I
speak not of the effective but of the formal
principle, whereby a thing is, and is called a being. Hence
follows the second condinon^njimely that the_ form and
matter combi ne toget her in one being, which is not the
case with the effective principle together with that to which
it
gives being. This is the being in which a composite
substance subsists, which is one in being, and consists of
matter and form. Now an intellectual substance, as proved