17. This procedure, if approved, will entail a distinction between psychic and bodily qualities, the latter belonging specifically to body.
If we decide to refer all souls to the higher, we are still at liberty to perform for Sensible qualities a division founded upon the senses themselves – the eyes, the ears, touch, taste, smell; and if we are to look for further differences, colours may be subdivided according to varieties of vision, sounds according to varieties of hearing, and so with the other senses: sounds may also be classified qualitatively as sweet, harsh, soft.
Here a difficulty may be raised: we divide the varieties of Substance and their functions and activities, fair or foul or indeed of any kind whatsoever, on the basis of Quality, Quantity rarely, if ever, entering into the differences which produce species; Quantity, again, we divide in accordance with qualities of its own: how then are we to divide Quality itself into species? what differences are we to employ, and from what genus shall we take them? To take them from Quality itself would be no less absurd than setting up substances as differences of substances.
How, then, are we to distinguish black from white? how differentiate colours in general from tastes and tangible qualities? By the variety of sense-organs? Then there will be no difference in the objects themselves.
But, waiving this objection, how deal with qualities perceived by the same sense-organ? We may be told that some colours integrate, others disintegrate the vision, that some tastes integrate, others disintegrate the tongue: we reply that, first, it is the actual experiences [of colour and taste, and not the sense-organs] that we are discussing and it is to these that the notions of integration and disintegration must be applied; secondly, a means of differentiating these experiences has not been offered.
It may be suggested that we divide them by their powers, and this suggestion is so far reasonable that we may well agree to divide the non-sensuous qualities, the sciences for example, on this basis; but we see no reason for resorting to their effects for the division of qualities sensuous. Even if we divide the sciences by their powers, founding our division of their processes upon the faculties of the mind, we can only grasp their differences in a rational manner if we look not only to their subject-matter but also to their Reason-Principles.
But, granted that we may divide the arts by their Reason-Principles and theorems, this method will hardly apply to embodied qualities. Even in the arts themselves an explanation would be required for the differences between the Reason-Principles themselves. Besides, we have no difficulty in seeing that white differs from black; to account for this difference is the purpose of our enquiry.