On The Soul
or encouraging scene. Again within the field of judgement itself we
find varieties, knowledge, opinion, prudence, and their opposites;
of the differences between these I must speak elsewhere.
Thinking is different from perceiving and is held to be in part
imagination, in part judgement: we must therefore first mark off the
sphere of imagination and then speak of judgement. If then imagination
is that in virtue of which an image arises for us, excluding
metaphorical uses of the term, is it a single faculty or disposition
relative to images, in virtue of which we discriminate and are
either in error or not? The faculties in virtue of which we do this
are sense, opinion, science, intelligence.
That imagination is not sense is clear from the following
considerations: Sense is either a faculty or an activity, e.g. sight
or seeing: imagination takes place in the absence of both, as e.g.
in dreams. (Again, sense is always present, imagination not. If actual
imagination and actual sensation were the same, imagination would be
found in all the brutes: this is held not to be the case; e.g. it is
not found in ants or bees or grubs. (Again, sensations are always
true, imaginations are for the most part false. (Once more, even in
ordinary speech, we do not, when sense functions precisely with regard
to its object, say that we imagine it to be a man, but rather when
there is some failure of accuracy in its exercise. And as we were
saying before, visions appear to us even when our eyes are shut.
Neither is imagination any of the things that are never in error: e.g.
knowledge or intelligence; for imagination may be false.
It remains therefore to see if it is opinion, for opinion may be
either true or false.
But opinion involves belief (for without belief in what we opine
we cannot have an opinion), and in the brutes though we often find
imagination we never find belief. Further, every opinion is
accompanied by belief, belief by conviction, and conviction by
discourse of reason: while there are some of the brutes in which we