A series of epochal events – the 2008 crisis, the pandemic, the war – are pushing us to rethink our institutions. Thus, especially in Italy, there has been a return to the question of what an institution is, how it can be and endure, how a tension lives in it between the “instituted” and the “instituting”, and how the instituting element must be valorised to ensure that associated life does not wither. Cornelius Castoriadis is one of the authors rediscovered in this debate, as he gave the category of institution not only a political, economic or social value, but an ontological one. However, his thought is still insufficiently known and its potential is still underestimated. The aim of this essay is to reconstruct the first phase of Castoriadis' thought, from his arrival in France to the publication of his most famous work in 1975. By traversing the years of political militancy, his adherence to and then his critique of Marxism, and by reconstructing his relationship with other intellectuals of the time - Sartre, Lefort, Lyotard, Debord, Merleau-Ponty - one can not only find the roots of the category of institution and grasp the profound significance of his project of autonomy, but also understand the relevance of his analysis and draw insights for today.
