f preserving
whatever receives it." Therefore we should not distinguish the
nutritive power from the generative.

_On the contrary,_ The Philosopher says (De Anima ii, 2,4) that the
operations of this soul are "generation, the use of food," and (cf.
_De Anima_ iii, 9) "growth."

_I answer that,_ The vegetative part has three powers. For the
vegetative part, as we have said (A. 1), has for its object the body
itself, living by the soul; for which body a triple operation of the
soul is required. One is whereby it acquires existence, and to this
is directed the _generative_ power. Another is whereby the living
body acquires its due quantity; to this is directed the
_augmentative_ power. Another is whereby the body of a living thing
is preserved in its existence and in its due quantity; to this is
directed the _nutritive_ power.

We must, however, observe a difference among these powers. The
nutritive and the augmentative have their effect where they exist,
since the body itself united to the soul grows and is preserved by the
augmentative and nutritive powers which exist in one and the same
soul. But the generative power has its effect, not in one and the same
body but in another; for a thing cannot generate itself. Therefore the
generative power, in a way, approaches to the dignity of the sensitive
soul, which has an operation extending to extrinsic things, although
in a more excellent and more universal manner; for that which is
highest in an inferior nature approaches to that which is lowest in
the higher nature, as is made clear by Dionysius (Div. Nom. vii).
Therefore, of these three powers, the generative has the greater
finality, nobility, and perfection, as the Philosopher says (De Anima
ii, 4), for it belongs to a thing which is already perfect to "produce
another like unto itself." And the generative power is served by the
augmentative and nutritive powers; and the augmentative power by the
nutritive.

Reply Obj. 1: Such forces are called natural, both because they
produce an effect like that of nature, which also gives existence,
quantity and preservation (although the above forces accomplish these
things in a more perfect way); and because those forces perform their
actions instrumentally, through the active and passive qualities,
which are the principles of natural actions.

Reply Obj. 2: Generation of inanimate things is entirely from an
extrinsic source; whereas the generation of living things is in a