This article examines the process of social marginalization and various insertion strategies. The author examines the various explanatory approaches to understanding the phenomenon of marginalization and social exclusion. After an historical detour describing the evolution of government aid and insurance policy, attention is directed to the current dynamic characterized by a return of vulnerability, the conjunction of an uncertain labour market and the fragility of relational supports. This article permits a rethinking of social reality not in terms of results but in terms of processes. The author also reflects on measures aimed at the reinsertion of marginalized populations. He examines the minimum insertion income (MII) not as a global solution, but as a temporary and necessary strategy.