The object of study of Psychiatry is hybrid, that is, it is both natural and social. It combines the methods of natural Sciences and those of social Sciences. Currently, Psychiatry is the branch of Medicine where epistemological and hermeneutical conflicts are more than evident; it is the medical discipline where this debate is most intense and problematic. However, the conceptual foundations of all these debates and conflicts are already preconfigured within the framework of the Greek philosophy of the Classical period. Without knowing these conceptual foundations it is impossible to adequately clarify all these conflicting aspects. During the period of Classical Greece it was the time when the conceptual foundations and rationale of the tekné iatriké (of which Psychiatry was and is a part) were established as well as the theoretical principles of epistemological issues such as the validity of categories, the controversy between diagnostic categories and psychopathological dimensions, the approach towards both subjectivity and phenomenology, the inquiry for Psychopathology, the concept of mental health, the possibilities and limits of the scientific method in Psychiatry, the role of Psychotherapy and, naturally, some key ethical issues in mental health, such as the existence of the stigma on psychiatric disorders and all of the problems raised by the coercitive practices. To answer all of these questions, a review of the literature on this topic has been made in this paper, as well as a discussion and analysis of the key points of the epistemological and ethical debate.