b, where we discriminate them, or regard them as unequal, is a relation of the pair of them, a dual relation. The generalization here founded upon Mr. Kempe’s paper will show us that contrast and comparison involve, in general, a relation of at least three objects, viz. ɑ and b, and something else that helps us to keep them apart, or that illustrates the point wherein they differ, or that helps to determine the sort, degree, or direction of their difference. This something may be an object of the exact character here ascribed to m. That is, it may be conceived as an object such that, if ɑ and b were to blend, or were to be viewed as equivalent, it would blend with both, or be viewed as equivalent to both. In such a case, the relationship emphasized by the contrast belongs not to the pair, ɑ and b, but to the triad, ɑ, b, and m. In other words, it is what one may technically name a triadic relation. The possibility of observing this relation is due to the fact that, since our discriminating attention is a voluntary act, possessed of its own internal meaning, we are able to see, by reflection, how one discrimination follows from another.
Let us look yet a little more closely at the considerations which come into view whenever we make any definite discrimination. I attend to ɑ and to b. I note that they are different. It follows, as we saw at the outset, that they differ in some character, and that they also, although of course in another respect, agree as to this same character. It may be color in which they differ. Then they agree also in having color. In magnitude, — then they agree in having magnitude. Tell me the character in which they differ, and I will at once under-
