Galen system is based on three pillars: the affected body part, the type of qualities imbalanced, and the degree of imbalance. Therefore, he only distinguishes between mental illness and impaired consciousness when there is a difference between these two entities in any of these three pillars. Thus, he distinguishes phrenitis from melancholia but not from mania. The emphasis on the system, on the other hand, enables him a very tight notion of disease, where symptoms, mechanisms, affected organ and treatment are closely linked.

4 Post-Hellenistic authors present a more compartmentalised idea of diseases in general and of impaired consciousness in particular. Unlike the Hippocratics, who barely discussed mental illness, these authors did distinguish impaired consciousness from mental illness through a classificatory system of dichotomic oppositions, additionally they discussed new conditions which are not mentioned in the HC. In most theorisations, perceptions play an increasingly relevant role to understand these conditions.

Contrary to mainstream scholarship’s opinion, the Hippocratic corpus presents many cases of impaired consciousness, but only a few of mental illness. By looking at three study cases, this chapter describes how these doctors understood conditions where patients act weirdly or were not their usual selves, and how they construed the notion of disease.

In the first chapter I introduce some methodological issues pertaining to the history of mental health: on the one hand, the issue of anachronism, the problem of retrospective diagnosis, on the other, the importance of maintaining intelligibility across cultures. When it comes to the ancient world, there are specific problems related to the nature of medical sources in Greek and Latin, and our limited access to the medical practices underlying them; in addition, the genre 'biography of disease' has its own pitfalls, namely those of attributing ‘essence’ to what appears, prima facie, to be most of all a construct: a disease concept or label such as phrenitis. Finally, in this chapter I consider the label phrenitis, its etymological meanings and the implications of the name vis-à-vis localization (chest? lungs? diaphragm? heart?) and mental life (mind? character? soul? mental capacities?). I also discuss the ‘Homeric’ appeal of the phrēn/phrenes, the name of the body part from which the label originates. The poetic archaism of phrēn/phrenes combined with its medical use made it both understandable as a generic term for mental life and specifically a ‘medical’ term to indicate the diaphragm, and contributed to making phrenitis a long-lasting disease concept.