Boulez’s status as a modern is rarely doubted. Yet he provided relatively little by way of explicit reflection on the concept of modernity. This chapter traces a path via Charles Baudelaire’s formulation in his essay, ‘The Painter of Modern Life’, and Michel Foucault’s commentary on it, to Foucault’s essay on Boulez himself, ‘Pierre Boulez, ou l’écran traversé’. There, Boulez is seen as motivated by ‘the necessity of a conjuncture’, an imperative for action demanded by whatever nexus of circumstances and contradictions confronts the individual in the present. The conjuncture, as further amplified by Louis Althusser, offers useful perspectives on Boulez’s modernity, which is often characterised as prescriptive and deterministic but which emerges here as relativist and perspectival, stressing contingency rather than inevitability. Above all, modernity comes to signify not a binding aesthetic but an enduring ethic, whose manifestations remain particular to the historical and problem contexts in which they arise.