DISTINCTION OF SENSE FROM INTELLECT
ERROR,
IMAGINATION AND OPINION
NOW, IF THE SOUL IS DEFINED PRINCIPALLY BY TWO differences, by motion in place and by what it is to understand, discern and sense, it would seem that both to understand and to judge are a kind of sense-perception,--for in either case the soul discerns and knows reality.§§ 615-16
The early philosophers, indeed, said that rational judgement and sensation were the same thing, as when Empedocles says: 'The will is increased in man in the present moment', and in another place: 'Whence it always affords them new objects of knowledge.' To the same purport is that line of Homer: 'The mind of mortals is such as the father of gods and men brings into light'. §§ 617-21
All these suppose the intellect to be something corporeal, like sensation, and that both sensing and judging are of 'like by like', as we explained at the beginning of this treatise.§§ 622-3
But they ought at the same time to have treated of error,--which is a state more natural to animals [than truth], and in which the soul spends the greater part of its time. So it must follow, either that all that seems to be really is (as some maintain) or that error is a contact with what is unlike--this being the contrary of knowing like by like.§§ 624-7
It would appear, however, that error and knowledge are the same with respect to contraries.§ 628
Now it should be evident that rational judgement and sensation are not the same. The latter is in all animals, the former in but few.§ 629
Nor again is understanding [the same as sensation]. It may be correct or incorrect,--correct as prudence, science and sound opinion; incorrect as the opposite of these. This is not the same as sensation. For sensation is always true of its own proper objects, and is found in all animals, whereas intelligence is sometimes accompanied by error, and is found in no species that lack reason.§§ 630-1
For imagination is other than both sensation and intellect. Yet it cannot occur without sensation, and without it there is no opinion.§ 632
It is evident that opinion and imagination are not identical. The latter state arises in us at will, as a picture before our eyes, like the imagery employed by those who cultivate memory training. But opinion is not within our power in this way; it must express the true or the false, of necessity.§ 633
Further, when we think that anything is arduous or fearful, we are at once emotionally affected; and likewise, if there be occasion for confidence. But in imagining, it is as though we were regarding in a picture things arduous or encouraging.§§ 634-5
These are, besides, the various modes of making a judgement: speculative science, opinion and prudence; with their contraries. Let the question of their differences be discussed elsewhere.§ 636