The hallucinogenic art of Michaux and other surrealists should never be regarded as advocating unbridled sensuous experimentation. The affects they generate may index absurdity, incongruity and comedy – they may ‘ridiculise’ our systematic thinking – but these affects thereby serve a more serious production of concepts. Through an abstemious aesthetics of existence Michaux becomes an ontologist of the prephilosophical sort. Carefully but ambiguously he explores the truths of matter, movement, body and modernity. As Deleuze saw clearly, the resulting ontology has strong affinities with that of Leibniz, though we have to insist on Simondon's transindividual dimension to obtain the full ontological purchase of hallucinogenic surrealisation.