PROP. VI.————
he constitution of knowledge as the necessary element is. And so, in one sense, it is. No knowledge is possible except through a union of these two factors. Therefore, neither part can be supposed to be wanting, without destroying the very conception of knowledge. But the explanation is this: although the contingent element cannot be abolished or left out, and is, therefore, in a certain sense necessary, it may nevertheless be changed. It is susceptible of infinite or indefinite variation. One particular (a tree, for instance) may be removed, but provided another particular (a house or something else) be placed before me, my knowledge continues to subsist. This element, then, is regarded as contingent, not because every form of it can be dispensed with—not because knowledge can take place without it, but solely because it can be varied. It is accidental because it is fluctuating. A cognition cannot be formed without some peculiar feature entering into its composition; but a cognition can be formed without this, or that, or any peculiar feature that can be named, entering into its composition; for the varieties of the particular constituent are inexhaustible. If one form of it disappears, another comes in its place. The peculiar part of cognition may always be other than it is: if it could not, there would be an end to every variety of knowledge, and consequently to knowledge itself. A flower may be apprehended instead of a book—a sound instead of a colour; any one particular
