(2) Again, the insufficiency of the simple identification of the thing with its qualities considered as a mere collection, may be illustrated by considering what the group of qualities must contain. The group of qualities is obviously never present in its entirety at any moment of experience. For the majority of what we call the qualities of a thing are simply the ways in which the “thing” behaves in the presence of various other things, its modes of reaction upon a number of stimuli. Now, at any moment of the “thing’s” existence it is only actually reacting upon a few of the possible stimuli, and thus only exhibiting a few of its qualities. The vast majority of its qualities are at any moment what Locke calls “powers,” _i.e._ ways in which it _would_ behave if certain absent conditions were fulfilled. Thus the thing to which we ascribe a number of predicates as its qualities is never the actual group of predicates themselves. Grass is green, but its greenness is not a fact in the dark; the sun is capable of melting the wax, and this capacity qualifies it permanently, but it does not actually melt the wax unless the wax is there, and various other conditions are also given; a man is temperamently choleric, but he is not actually at every moment of his existence in a passion. He is only predisposed to fly into a passion readily on the occurrence of provocation. Most of a thing’s qualities thus are mere possibilities; the nature of the thing is to act in this or that way under certain definite conditions which may or may not be realised in actual existence. Thus the collection of qualities with which Phenomenalism identifies a thing has itself no real existence as a collection. The collection is just as much a “fiction of the mind” as the unity which we attribute to it. Yet the fact that the thing’s qualities are mainly mere possibilities does not destroy the existence of the thing. It actually is, and is somehow qualified by these possibilities. And for that very reason its existence cannot be identified with the actual realisation of these possibilities in a group or collection of events. We might add as a further consideration, that the number of such possibilities is indefinite, including not only the ways in which the thing has behaved or will behave on the occurrence of conditions at present non-existent, but also all the ways in which it would behave on the occurrence of conditions which are _never_ realised in actual existence. But the previous argument is already in itself sufficient, the moment its significance is fairly grasped, to dispose of the notion that anything can be merely identical with a group of actually existing sensible qualities. The being of the things must be sought not in the actual existence of the group of sensible qualities, but in the law or laws stating the qualities which would be exhibited in response to varying sets of conditions.[84]