“Spinoza: The Velocities of Thought” was a 15-lecture seminar given from December 1980 to March 1981. In this seminar, Deleuze revisits his examination of Baruch Spinoza’s philosophy. Deleuze had previously published two books on Spinoza: Expressionism in Philosophy: Spinoza (Spinoza et le problème de l’expression, 1968), and Spinoza: Practical Philosophy (Spinoza – Philosophie pratique, 1970, 2nd ed. 1981). The majority of these lectures were given the same year as the publication of the second edition of the latter title, and hence these sessions were clearly informed by this new editorial preparation. The Seminar included here provides a sixteenth session, from 1978, on the theme of “continuous variation” that addresses Spinoza.