e operations are in the soul as
their subject. But some operations of the soul are performed by means
of corporeal organs; as sight by the eye, and hearing by the ear. And
so it is with all the other operations of the nutritive and sensitive
parts. Therefore the powers which are the principles of these
operations have their subject in the composite, and not in the soul
alone.

Reply Obj. 1: All the powers are said to belong to the soul, not as
their subject, but as their principle; because it is by the soul that
the composite has the power to perform such operations.

Reply Obj. 2: All such powers are primarily in the soul, as compared
to the composite; not as in their subject, but as in their principle.

Reply Obj. 3: Plato's opinion was that sensation is an operation
proper to the soul, just as understanding is. Now in many things
relating to Philosophy Augustine makes use of the opinions of Plato,
not asserting them as true, but relating them. However, as far as the
present question is concerned, when it is said that the soul senses
some things with the body, and some without the body, this can be
taken in two ways. Firstly, the words "with the body or without the
body" may determine the act of sense in its mode of proceeding from
the sentient. Thus the soul senses nothing without the body, because
the action of sensation cannot proceed from the soul except by a
corporeal organ. Secondly, they may be understood as determining the
act of sense on the part of the object sensed. Thus the soul senses
some things with the body, that is, things existing in the body, as
when it feels a wound or something of that sort; while it senses some
things without the body, that is, which do not exist in the body, but
only in the apprehension of the soul, as when it feels sad or joyful
on hearing something.
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SIXTH ARTICLE [I, Q. 77, Art. 6]

Whether the Powers of the Soul Flow from Its Essence?

Objection 1: It would seem that the powers of the soul do not flow
from its essence. For different things do not proceed from one
simple thing. But the essence of the soul is one and simple. Since,
therefore, the powers of the soul are many and various, they cannot
proceed from its essence.

Obj. 2: Further, that from which a thing proceeds is its cause.
But the essence of the soul cannot be said to be the cause of the
powers; as is clear if one considers the different kinds of causes.
Therefore the powers of