Book 4
26
And again in the case of the senses themselves, our perception of a foreign object and of an object proper to a given sense, or of a kindred object and of an actual object of that sense itself, is not equally reliableAn object of taste is foreign to the sense of sight; a thing may look sweet without tasting sweet. Similarly although the senses of taste and smell (and therefore their objects) are kindred (Aristot. De Sensu 440b 29), in judging tastes the sense of taste is the more reliable.; but in the case of colors sight, and not taste, is authoritative, and in the case of flavor taste, and not sight. But not one of the senses ever asserts at the same time of the same object that it is so and not so.
27
Nor even at another time does it make a conflicting statement about the quality, but only about that to which the quality belongs. I mean, e.g., that the same wine may seem, as the result of its own change or of that of one’s body, at one time sweet and at another not; but sweetness, such as it is when it exists, has never yet changed, and there is no mistake about it, and that which is to be sweet is necessarily of such a nature.
28
Yet all these theories destroy the possibility of anything’s existing by necessity, inasmuch as they destroy the existence of its essence; for the necessary cannot be in one way and in another; and so if anything exists of necessity, it cannot be both so and not so.
