This thesis argues that the concept of contingency plays a central role in Althusser's recasting of Marxist philosophy and in his attempt to free the Marxist conception of history from concepts such as teleology, necessity and origin. It is critically placed both against those readings that see the emergence of the problematic of contingency only in the late Althusserm and to the most recent attempts to establish a straightforward continuity in Althusser's work. Drawing on published and unplublished material and covering (...) the entirety of Althusser's philosophical itinerary, the thesis seeks both to unearth the latent presence of this problematic, and its various implications, at each stage in the development of his work. It seeks to clarify, in a systematic way, the conceptual consequences of Althusser's commitment to contingency to the received understanding of his conceptions of structural change, ideology and political action. In particular, it argues that the standpoint of contingency allows us to locate in Althusser's 'Structural Marxism' the emergence of a 'logic of irruption' and structurally under-determined development of becoming. By emphasising this logic of contingency, it then seeks to produce a more nuanced assessment of his theory of ideology through the introduction of the concept of 'overinterpellation'. It finally attempts to distinguish two moments in the emergence of a materialism of contingency, first political and then philosophical; the problematic coexistence of these two aspects helps to account for the unstable charactoer of Althusser's late philosophical project. (shrink)