OUR IDEAS OF SUBSTANCE, CAUSALITY AND IDENTITY
§1 . In following Locke through his treatment of our ideas of modes, we have been chiefly concerned in watching the gradual breakdown in his hands of the composition theory. The ideas of substance, causality and identity, which form the subject of the present chapter, raise problems, and involve difficulties, of a different kind. Causality and identity are for Locke ideas of relation, and such are admittedly not the result of composition. And while adhering to the current view that substance is in itself an absolute, unaffected by relations, he reaches the paradoxical conclusion that the only idea we can form of this absolute is a relative one.
The possibility of ideas of relation being once admitted, Locke is, therefore, no longer under an obligation to make his account of our ideas of these specific relations square with the presuppositions of the composition theory. We shall find, however, that in dealing with our ideas of substances, Locke's thought is constantly hampered by the strictly analogous assumption of the current metaphysics. For, just as the composition theory, in the form in which it was put forward by him, sought to resolve the contents of our ideas into a number of separate and self-identical units of experience, so the metaphysics, which he inherited, held that reality consists of a number of separate and