This paper considers the trajectory of Althusser's Spinozism pre- and post-May ‘68. Where Althusser's application of Spinoza would often lead him into unknown or non-Marxist territory, one alternative way to think this relation is through the figure of Mao, whose concept of non-antagonistic contradiction I propose to read in terms of Spinoza's “determinate negation.” Although not going so far as to suggest that a certain combination of Mao and Spinoza would have enabled Althusser to “complete” Marx, this paper speculates on (...) this omission from his work and what positive insights we can draw from it retrospectively for developing Althusser's political philosophy. (shrink)