Starting with Gilbert Simondon's theory of the individual (singular and collective) and its genesis, developed in his book L'individuation psychique et collective, this article discusses the principle of individuation and the critique of finalism. Simondon distinguishes and yet strictly binds together the two individuations that he calls psychique and collective, which is necessary, he argues, to avoid the double failure of psychologism and sociologism, by which he means the doctrines that assign a fixed (ontological) identity to man and his mind, on the one hand, and to society, on the other. Both psychologism and sociologism, according to Simondon, fail to understand their only reality, which is first and foremost relational. Influenced by Simondon's ontology, Gilles Deleuze's concept of nomadism is taken up in order to develop the idea of a principle of individuation intended as a critique of teleology. The question of individuation is thus referred to its ontological roots in the conflict between Aristotelian metaphysics (priority of act over power [potentia] and of final cause over efficient and material causes) and Spinozist metaphysics (power [potentia] existing only in act, absolute immanence, radical criticism of every teleology). This essay shows what is at stake between the two authors and what Deleuze could not have derived from Simondon, which Del Lucchese calls a Spinozistic problematic.