Whether the Powers Are Distinguished by Their Acts and Objects?
Objection 1: It would seem that the powers of the soul are not
distinguished by acts and objects. For nothing is determined to its
species by what is subsequent and extrinsic to it. But the act is
subsequent to the power; and the object is extrinsic to it. Therefore
the soul's powers are not specifically distinct by acts and objects.
Obj. 2: Further, contraries are what differ most from each other.
Therefore if the powers are distinguished by their objects, it follows
that the same power could not have contrary objects. This is clearly
false in almost all the powers; for the power of vision extends to
white and black, and the power to taste to sweet and bitter.
Obj. 3: Further, if the cause be removed, the effect is removed.
Hence if the difference of powers came from the difference of objects,
the same object would not come under different powers. This is clearly
false; for the same thing is known by the cognitive power, and desired
by the appetitive.
Obj. 4: Further, that which of itself is the cause of anything, is
the cause thereof, wherever it is. But various objects which belong
to various powers, belong also to some one power; as sound and color
belong to sight and hearing, which are different powers, yet they
come under the one power of common sense. Therefore the powers are
not distinguished according to the difference of their objects.
_On the contrary,_ Things that are subsequent are distinguished by
what precedes. But the Philosopher says (De Anima ii, 4) that "acts
and operations precede the powers according to reason; and these
again are preceded by their opposites," that is their objects.
Therefore the powers are distinguished according to their acts and
objects.
_I answer that,_ A power as such is directed to an act. Wherefore we
seek to know the nature of a power from the act to which it is
directed, and consequently the nature of a power is diversified, as
the nature of the act is diversified. Now the nature of an act is
diversified according to the various natures of the objects. For every
act is either of an active power or of a passive power. Now, the
object is to the act of a passive power, as the principle and moving
cause: for color is the principle of vision, inasmuch as it moves the
sight. On the other hand, to the act of an active power the object is
a term and end; as the object of the power of growth is perfect
quantity, which is the end of growth. Now, from these two things an
act receives its species, namely, from its principle, or from its end
or term; for the act of heating differs from the act of cooling, in
this, that the former proceeds from something hot, which is the active
principle, to heat; the latter from something cold, which is the
active principle, to cold. Therefore the powers are of necessity
distinguished by their acts and objects.
Nevertheless, we must observe that things which are accidental do not
change the species. For since to be colored is accidental to an
animal, its species is not changed by a difference of color, but by a
difference in that which belongs to the nature of an animal, that is
to say, by a difference in the sensitive soul, which is sometimes
rational, and sometimes otherwise. Hence "rational" and "irrational"
are differences dividing animal, constituting its various species. In
like manner therefore, not any variety of objects diversifies the
powers of the soul, but a difference in that to which the power of its
very nature is directed. Thus the senses of their very nature are
directed to the passive quality which of itself is divided into color,
sound, and the like, and therefore there is one sensitive power with
regard to color, namely, the sight, and another with regard to sound,
namely, hearing. But it is accidental to a passive quality, for
instance, to something colored, to be a musician or a grammarian,
great or small, a man or a stone. Therefore by reason of such
differences the powers of the soul are not distinct.
Reply Obj. 1: Act, though subsequent in existence to power, is,
nevertheless, prior to it in intention and logically; as the end is
with regard to the agent. And the object, although extrinsic, is,
nevertheless, the principle or end of the action; and those
conditions which are intrinsic to a thing, are proportionate to its
principle and end.
Reply Obj. 2: If any power were to have one of two contraries as such
for its object, the other contrary would belong to another power. But
the power of the soul does not regard the nature of the contrary as
such, but rather the common aspect of both contraries; as sight does
not regard white as such, but as color. This is because of two
contraries one, in a manner, includes the idea of the other, since
they are to one another as perfect and imperfect.
Reply Obj. 3: Nothing prevents things which coincide in subject, from
being considered under different aspects; therefore they can belong
to various powers of the soul.
Reply Obj. 4: The higher power of itself regards a more universal
formality of the object than the lower power; because the higher a
power is, to a greater number of things does it extend. Therefore
many things are combined in the one formality of the object, which
the higher power considers of itself; while they differ in the
formalities regarded by the lower powers of themselves. Thus it is
that various objects belong to various lower powers; which objects,
however, are subject to one higher power.
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