the soul do not flow from its essence.

Obj. 3: Further, emanation involves some sort of movement. But
nothing is moved by itself, as the Philosopher proves (Phys. vii,
1,2); except, perhaps, by reason of a part of itself, as an animal
is said to be moved by itself, because one part thereof moves and
another is moved. Neither is the soul moved, as the Philosopher
proves (De Anima i, 4). Therefore the soul does not produce its
powers within itself.

_On the contrary,_ The powers of the soul are its natural properties.
But the subject is the cause of its proper accidents; whence also it
is included in the definition of accident, as is clear from _Metaph._
vii (Did. vi, 4). Therefore the powers of the soul proceed from its
essence as their cause.

_I answer that,_ The substantial and the accidental form partly agree
and partly differ. They agree in this, that each is an act; and that
by each of them something is after a manner actual. They differ,
however, in two respects. First, because the substantial form makes
a thing to exist absolutely, and its subject is something purely
potential. But the accidental form does not make a thing to exist
absolutely but to be such, or so great, or in some particular
condition; for its subject is an actual being. Hence it is clear that
actuality is observed in the substantial form prior to its being
observed in the subject: and since that which is first in a genus is
the cause in that genus, the substantial form causes existence in its
subject. On the other hand, actuality is observed in the subject of
the accidental form prior to its being observed in the accidental
form; wherefore the actuality of the accidental form is caused by the
actuality of the subject. So the subject, forasmuch as it is in
potentiality, is receptive of the accidental form: but forasmuch as
it is in act, it produces it. This I say of the proper and _per se_
accident; for with regard to the extraneous accident, the subject is
receptive only, the accident being caused by an extrinsic agent.
Secondly, substantial and accidental forms differ, because, since that
which is the less principal exists for the sake of that which is the
more principal, matter therefore exists on account of the substantial
form; while on the contrary, the accidental form exists on account of
the completeness of the subject.

Now it is clear, from what has been said (A. 5), that either the
subject of the soul's powers is the soul itself