In Althusser's late philosophy - aleatory materialism - there are two main theses: the contingency of necessity and the necessity of contingency. The paper aims at elucidating and discussing both. First, the relationship between aleatory materialism and Althusser's previous philosophy is clarified. Second, the meaning of aleatory encounter is exposed. Third, the definition of necessity as “the becoming-necessary of the encounter of contingencies” is explained. Finally, the necessity of contingency is discussed through a comparison with Meillassoux’s speculative thought.
