ABSTRACT Cornelius Castoriadis is one of the most important democratic thinkers in the second half of the twentieth century, and his theory of autonomy and the self-instituted character of society are fundamental to many post-Marxist theories of democracy. The role of the council system in Castoriadis' work, though, has rarely been investigated, and his analysis of the twentieth century workers' councils of has seldom been connected to his important concepts of autonomy and the instituting power. The article remedies this lack (...) of engagement with Castoriadis' analysis of the council system and argues that the emergence of workers' councils in Castoriadis' own lifetime, during the Hungarian Revolution of 1956, provided a crucial impetus for his formulation of a theory of autonomy. Moreover, the article argues that the role of the council system in Castoriadis' work provides a privileged vantage point in order to nuance the critique – voiced by for example Jürgen Habermas and Claude Lefort – that Castoriadis exclusively valorise constituent politics without properly appreciating the importance of ordinary politics. Contrary to this interpretation, the article demonstrates how Castoriadis look to the councils to understand how democratic politics entails both freedom to act anew and the need for institutional structure. (shrink)