Abstract

In What Is Philosophy? Deleuze and Guattari understand concepts in a very unconventional way. One of the central aspects of their theory is that concepts are self-referential and should not be understood in terms of any form of reference or representation. Instead, concepts are complex “assemblages” interacting on a “plane of immanence.” I argue that we can best understand this theory through the philosophy of Spinoza. The latter understands thought and ideas through the model of physical bodies. Spinoza’s theory of thought is, as François Zourabichvili says, a “physics of thought.” I do not only call upon Spinoza to elucidate the general approach of Deleuze and Guattari; I also use Spinoza’s notions of modal essence and existence, interpreted by Deleuze in terms of intensity and extensity, to expound the details of their distinction between concepts and propositions.