ral movement be from
God as the First Mover, inasmuch as nature is an instrument of God
moving it: so it is not contrary to the essence of a voluntary act,
that it proceed from God, inasmuch as the will is moved by God.
Nevertheless both natural and voluntary movements have this in common,
that it is essential that they should proceed from a principle within
the agent.
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SECOND ARTICLE [I-II, Q. 6, Art. 2]

Whether There Is Anything Voluntary in Irrational Animals?

Objection 1: It would seem that there is nothing voluntary in
irrational animals. For a thing is called "voluntary" from _voluntas_
(will). Now since the will is in the reason (De Anima iii, 9), it
cannot be in irrational animals. Therefore neither is there anything
voluntary in them.

Obj. 2: Further, according as human acts are voluntary, man is said
to be master of his actions. But irrational animals are not masters
of their actions; for "they act not; rather are they acted upon," as
Damascene says (De Fide Orth. ii, 27). Therefore there is no such
thing as a voluntary act in irrational animals.

Obj. 3: Further, Damascene says (De Fide Orth. 24) that "voluntary
acts lead to praise and blame." But neither praise nor blame is due
to the acts of irrational minds. Therefore such acts are not
voluntary.

_On the contrary,_ The Philosopher says (Ethic. iii, 2) that "both
children and irrational animals participate in the voluntary." The
same is said by Damascene (De Fide Orth. 24) and Gregory of Nyssa
[*Nemesius, De Nat. Hom. xxxii.].

_I answer that,_ As stated above (A. 1), it is essential to the
voluntary act that its principle be within the agent, together with
some knowledge of the end. Now knowledge of the end is twofold;
perfect and imperfect. Perfect knowledge of the end consists in not
only apprehending the thing which is the end, but also in knowing it
under the aspect of end, and the relationship of the means to that
end. And such knowledge belongs to none but the rational nature. But
imperfect knowledge of the end consists in mere apprehension of the
end, without knowing it under the aspect of end, or the relationship
of an act to the end. Such knowledge of the end is exercised by
irrational animals, through their senses and their natural estimative
power.

Consequently perfect knowledge of the end leads to the perfect
voluntary; inasmuch as, having apprehended the end, a man can, from
deliberating about the end