In the history of madness, two events signal this change with singular clarity: in 1657, the founding of the Hôpital Général, and the Great Confinement of the poor; and in 1794, the liberation of the mad in chains at Bicêtre. Between these two singular and symmetrical events, something happened, whose ambiguity has perplexed historians of medicine: blind repression in an absolutist regime, according to some, and, according to others, the progressive discovery, by science and philanthropy, of madness in its positive truth. In fact, beneath these reversible meanings, a structure was taking shape, which did not undo that ambiguity but was decisive for it. This structure explains the passage from the medieval and humanist experience of madness to the experience that is our own, which confines madness in mental illness.