I consider some ways in which the Copy Principle (CP) and Hume's nominalism impinge on one another, arguing for the following claims. First, Hume's argument against indeterminate ideas isn't cogent even if the CP is accepted. But this does not vindicate Locke: the imagistic conception of ideas, presupposed by the CP, 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, that which takes the CP 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.