Mill holds a metaphysical theory about the nature of things which is of the sensationalist or phenomenalist variety, and which he derives admittedly from the idealism of Berkeley. This metaphysical theory is introduced into a discussion in which he is attempting something different, namely, to offer a rival psychological account to Hamilton's intuitionist one of how it is that men possess that familiar but complex conception, Nature or the external world. It will be convenient to consider his psychological theory first.

In this paper, I consider some ways in which the Copy Principle and Hume’s nominalism impinge on one another, concluding that the marriage is not a happy one. I argue for the following claims. First, Hume’s argument against indeterminate ideas isn’t cogent even if the Copy Principle is accepted. But this does not vindicate Locke: the imagistic conception of ideas, presupposed by the Copy Principle, will force Locke to accept something like Hume’s view of the way general terms function, the (...) availability of abstract ideas notwithstanding. Second, Hume’s discussion of nominalism provides support for the “old Hume” interpretation, which takes the Copy Principle to be a criterion of meaningfulness, as against the “new Hume” reading, according to which it constrains what we can know. Finally, nominalism forces Hume to adopt a more complicated theory of ideas. (shrink)