In recent decades, respect for patient autonomy has progressively established itself as a reference principle in biomedical ethics. At the same time, there has been a proliferation of different interpretations and definitions of this concept, which have led to ideological clashes even violent, as in recent cases of euthanasia, the focus of media attention. In the face of such a rich and diversified debate, this study proposes a reconstruction of the genesis of the notion of autonomy in biomedical ethics and a significant reinterpretation of this concept through the critical analysis of different philosophical models. The volume concludes with an examination of decisions regarding people with reduced or evanescent autonomy, with the aim of showing how the dilemma of such decisions can be deciphered starting from a conception of autonomy as a "relationship of authority".