The OneAlain Badiou's 19831984 lecture series on "the One" is the earliest of his seminars that he has chosen to publish. It focuses on the philosophical concept of oneness in the works of Descartes, Plato, and Kant a crucial foil for his signature metaphysical concept, the multiple. Badiou declares that there is no "One": there is no fundamental unit of being; being is inherently multiple. What is novel in Badiou's view of multiplicity is his reliance on