 Berkeley offers both epistemological and metaphysical arguments for his immaterialism. His epistemological arguments begin from the premise that ideas and only ideas are the objects of human knowledge, a presupposition that he at least considered uncontroversial. Although his taxonomy of the different kinds of ideas deviate in ways that are not of interest here from Locke’s classification, he agrees with Locke that ideas exist only “in the mind” (1710: Part I, §2). He takes the mind to be a “perceiving, active being” which itself is not 