is particular thing."

Reply Obj. 2: Aristotle wrote those words as expressing not his own
opinion, but the opinion of those who said that to understand is to
be moved, as is clear from the context. Or we may reply that to
operate _per se_ belongs to what exists _per se._ But for a thing to
exist _per se,_ it suffices sometimes that it be not inherent, as an
accident or a material form; even though it be part of something.
Nevertheless, that is rightly said to subsist _per se,_ which is
neither inherent in the above sense, nor part of anything else. In
this sense, the eye or the hand cannot be said to subsist _per se_;
nor can it for that reason be said to operate _per se._ Hence the
operation of the parts is through each part attributed to the whole.
For we say that man sees with the eye, and feels with the hand, and
not in the same sense as when we say that what is hot gives heat by
its heat; for heat, strictly speaking, does not give heat. We may
therefore say that the soul understands, as the eye sees; but it is
more correct to say that man understands through the soul.

Reply Obj. 3: The body is necessary for the action of the intellect,
not as its origin of action, but on the part of the object; for the
phantasm is to the intellect what color is to the sight. Neither
does such a dependence on the body prove the intellect to be
non-subsistent; otherwise it would follow that an animal is
non-subsistent, since it requires external objects of the senses
in order to perform its act of perception.
_______________________

THIRD ARTICLE [I, Q. 75, Art. 3]

Whether the Souls of Brute Animals Are Subsistent?

Objection 1: It would seem that the souls of brute animals are
subsistent. For man is of the same genus as other animals; and,
as we have just shown (A. 2), the soul of man is subsistent.
Therefore the souls of other animals are subsistent.

Obj. 2: Further, the relation of the sensitive faculty to sensible
objects is like the relation of the intellectual faculty to
intelligible objects. But the intellect, apart from the body,
apprehends intelligible objects. Therefore the sensitive faculty,
apart from the body, perceives sensible objects. Therefore, since
the souls of brute animals are sensitive, it follows that they are
subsistent; just as the human intellectual soul is subsistent.

Obj. 3: Further, the soul of brute animals moves the body. But the
body is not a mover, but is moved. Therefore the soul of br