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.