Why does Gilles Deleuze write about the cinema as a philosopher?Despite their title, Gilles Deleuze's 'Cinema' books are not 'about' the cinema: they are works of philosophy first and foremost, even if this has yet to be fully recognised. Deleuze turns to the cinema in order to address specific philosophical problems - precisely because the formal resources of the cinema enable it to 'think' the relation between movement and duration in ways that philosophy cannot. Allan James Thomas unpacks the nature of the philosophical problems that Deleuze turns to the cinema to resolve, and shows both how and why the resources of the cinema enable him to do so where philosophy alone cannot. Thomas offers new insights into the conceptual underpinnings both of the Cinema books themselves and of the trajectory of Deleuzian philosophy as a whole.