Locke seems to hold that we have knowledge of the existence of external objects through sensation. Two problems face Locke's account. The first problem concerns the logical form of knowledge of real existence. Locke defines knowledge as the perception of the agreement or disagreement between ideas. However, perceiving agreements between ideas seems to yield knowledge only of analytic truths, not propositions about existence. The second problem concerns the epistemic status of sensitive knowledge: How could the senses yield certain knowledge? This (...) essay argues that the key to solving both problems is Locke's claim that simple ideas are all real, adequate, and true. This explains why, on Locke's view, we have certain knowledge through the senses. It also explains how sensitive knowledge can consist in perceiving an agreement between ideas: perceived agreements among simple ideas of sensation are guaranteed to track relations that obtain among really existing things. (shrink)

Locke tells us that his purpose in An Essay Concerning Human Understanding is “to inquire into the original, certainty, and extent of human knowledge, together with the grounds and degrees of belief, opinion, and assent”. He provides a characterization of general human knowledge as universal truths in propositional form. In doing this he presupposes a striking doctrine about the “extent” of man's general knowledge, and he draws freely upon a theory meant to explain both the materials out of which this (...) knowledge is constructed and the way in which it is constructed. He holds that the “certainty” which characterizes general knowledge is obtained only if we proceed from the right materials or foundations in the right way, and that the right foundations themselves can only be obtained in one specific way. In this study I try to show how much more Cartesian Locke is than many commentators would allow. I argue that on Locke's own view the way to obtain the foundations for general knowledge is that of Cartesian analysis, and the way to construct general knowledge once these foundations have been obtained is that of Cartesian synthesis. (shrink)