need to perceive such intentions, which the
exterior sense does not perceive. And some distinct principle is
necessary for this; since the perception of sensible forms comes by an
immutation caused by the sensible, which is not the case with the
perception of those intentions.

Thus, therefore, for the reception of sensible forms, the "proper
sense" and the _common sense_ are appointed, and of their distinction
we shall speak farther on (ad 1, 2). But for the retention and
preservation of these forms, the "phantasy" or "imagination" is
appointed; which are the same, for phantasy or imagination is as it
were a storehouse of forms received through the senses. Furthermore,
for the apprehension of intentions which are not received through the
senses, the "estimative" power is appointed: and for the preservation
thereof, the "memorative" power, which is a storehouse of such-like
intentions. A sign of which we have in the fact that the principle of
memory in animals is found in some such intention, for instance, that
something is harmful or otherwise. And the very formality of the past,
which memory observes, is to be reckoned among these intentions.

Now, we must observe that as to sensible forms there is no difference
between man and other animals; for they are similarly immuted by the
extrinsic sensible. But there is a difference as to the above
intentions: for other animals perceive these intentions only by some
natural instinct, while man perceives them by means of coalition of
ideas. Therefore the power by which in other animals is called the
natural estimative, in man is called the "cogitative," which by some
sort of collation discovers these intentions. Wherefore it is also
called the "particular reason," to which medical men assign a certain
particular organ, namely, the middle part of the head: for it compares
individual intentions, just as the intellectual reason compares
universal intentions. As to the memorative power, man has not only
memory, as other animals have in the sudden recollection of the past;
but also "reminiscence" by syllogistically, as it were, seeking for a
recollection of the past by the application of individual intentions.
Avicenna, however, assigns between the estimative and the imaginative,
a fifth power, which combines and divides imaginary forms: as when
from the imaginary form of gold, and imaginary form of a mountain, we
compose the one form of a golden mountain, which we have never seen