Deleuze began his philosophical career writing studies of various classic figures in the history of philosophy. His first book, published in 1953, was a study of Hume, and it was followed by a series of monographs on Nietzsche (1962), Kant (1963), Bergson (1966), and Spinoza (1968), which Deleuze continued in the 1980s, when he wrote his studies of Foucault (1986) and Leibniz (1988). In the intervening years he wrote his magnum opus, Difference and Repetition (1968), as well as his two-volume work of political philosophy, Capitalism and Schizophrenia (1972, 1980), co-authored with Félix Guattari. But what is the relation between these two sets of writings – one in the history of philosophy and the other in philosophy proper? Deleuze said that he considered Difference and Repetition to be a work in metaphysics. “I feel myself to be a pure metaphysician,” he once claimed. “Bergson says that modern science hasn’t found its metaphysics, the metaphysics it would need. It is this metaphysics that interests me.” Yet the history of philosophy seems to be littered with the detritus of outdated metaphysical systems, including some of the very systems that Deleuze analyzed in his historical monographs. “If we consider any scheme of philosophic categories as one complex assertion,” Whitehead once wrote, “and apply to it the logician’s alternative, true or false, the answer must be that the scheme is false.” Deleuze seems to have agreed with Bergson and Whitehead that metaphysics provides a schema of concepts adequate to both experience and science, and he attributed a complete positivity to “the power of the false” found in such systems. But what role did Deleuze’s work in the history of philosophy play in the development of his heterogenetic and differential metaphysical system?