lect. The
reason therefore why Socrates understands is not because he is moved
by his intellect, but rather, contrariwise, he is moved by his
intellect because he understands. Secondly, because since Socrates is
an individual in a nature of one essence composed of matter and form,
if the intellect be not the form, it follows that it must be outside
the essence, and then the intellect is the whole Socrates as a motor
to the thing moved. Whereas the act of intellect remains in the agent,
and does not pass into something else, as does the action of heating.
Therefore the action of understanding cannot be attributed to Socrates
for the reason that he is moved by his intellect. Thirdly, because the
action of a motor is never attributed to the thing moved, except as to
an instrument; as the action of a carpenter to a saw. Therefore if
understanding is attributed to Socrates, as the action of what moves
him, it follows that it is attributed to him as to an instrument. This
is contrary to the teaching of the Philosopher, who holds that
understanding is not possible through a corporeal instrument (De Anima
iii, 4). Fourthly, because, although the action of a part be
attributed to the whole, as the action of the eye is attributed to a
man; yet it is never attributed to another part, except perhaps
indirectly; for we do not say that the hand sees because the eye sees.
Therefore if the intellect and Socrates are united in the above
manner, the action of the intellect cannot be attributed to Socrates.
If, however, Socrates be a whole composed of a union of the intellect
with whatever else belongs to Socrates, and still the intellect be
united to those other things only as a motor, it follows that Socrates
is not one absolutely, and consequently neither a being absolutely,
for a thing is a being according as it is one.

There remains, therefore, no other explanation than that given by
Aristotle--namely, that this particular man understands, because the
intellectual principle is his form. Thus from the very operation of
the intellect it is made clear that the intellectual principle is
united to the body as its form.

The same can be clearly shown from the nature of the human species.
For the nature of each thing is shown by its operation. Now the proper
operation of man as man is to understand; because he thereby surpasses
all other animals. Whence Aristotle concludes (Ethic. x, 7) that the
ultimate happiness of man must consist in