Self-regulation, government intervention, networking: transformations of the social state in europe (the cases of hiv/aids, alcohol and drug abuse) A reflection about the development of the social state and its recent changes proceeds from the analysis of the policies carried out in the areas of alcohol and illegal drug abuse and HIV/AIDS. A historical reconstruction provides a view of the transformations of government activity in this century, which has seen the birth and the decline of the social state, as well as the development of new forms of government action aimed at moderating actors. Comparing the responses to these social problems in terms of public policies, the authors observe phases of divergence and convergence corresponding to a changing demarcation between the sphere of politics and that of knowledge.