Combines historical research and philosophical analysis to cast light on why and how Cartesianism failed as a complete metaphysical system. Far more radical in its conclusions than his 1966 study The Downfall of Cartesianism (a slightly revised version of which forms the main body of the current work), Watson argues that Descartes's ontology is incoherent and vacuous, his epistemology deceptive, and his theology unorthodox--indeed, that Descartes knows nothing.