For Berkeley, a thing's existence 'esse' is nothing more than its being perceived 'as that thing'. It makes no sense to ask (with Samuel Johnson) about the 'esse' of the mind or the specific act of perception, for that would be like asking what it means for existence to exist. Berkeley's "existere is percipi or percipere" (NB 429) thus carefully adopts the scholastic distinction between 'esse' and 'existere' ignored by Locke and others committed to a substantialist notion of mind. Following (...) the Stoics, Berkeley proposes that, 'as' the existence of ideas, minds "subsist" rather than "exist" and, accordingly, cannot be identified as independently existing things. (shrink)

Behind Berkeley looms the figure of Descartes. For though Descartes did not directly influence Berkeley as much as did Locke, Malebranche, and Bayle, the points at which these three most affected Berkeley’s thinking were often just those at which they were themselves reacting to Descartes’ doctrines. This is most apparent in the question of the existence of the material world, for it was Descartes who had made that a central topic of discussion in the seventeenth century. When Malebranche sought to (...) show that we cannot be certain matter exists, it was Descartes’ proof he had to combat. When Bayle used Zeno’s paradoxes to try to prove that extension cannot exist, it was Descartes’ concept of matter he was chiefly aiming at. When Locke argued for a degree of cognition “going beyond bare probability, and yet not reaching perfectly to either [intuitive or demonstrative] certainty,” it was because, while he agreed with Malebranche that Descartes did not and could not demonstrate the existence of bodies, he hoped for better evidence of it than just the high probability proffered by Malebranche. The origin and growth of Berkeley’s immaterialism owed enough to these reactions to the Cartesian proof of the material world that I think it safe to say that, without Descartes, the philosophy of Berkeley, had there been such, would be very unlike the one we know. But I have elsewhere examined the relation of Cartesianism to the denial of material substance and am not going to say more of it here. Instead, I want to look at the relation between Descartes’ and Berkeley’s concepts of mental substance, for there their agreement is almost as complete as is their disagreement about material substance. (shrink)