This book looks at ancient medical descriptions of patients with disturbed behaviours, altered sleep and swoons (three presentations of what we nowadays designate as impaired consciousness), in order to explore if and how their authors conceived the notion of consciousness. Undoubtedly, such a construct intersects with diverse non-technical discourses (including philosophy, religion, literary and art representations), and medical writers – as individuals immersed in their respective societies – were not alien to them. Nevertheless, my analysis will mainly focus on the scientific debate (with only minor digressions about other areas of thought and culture, whenever they are key to understanding the textual evidence).

The rationale for such a decision is that doctors’ subject matter is eminently practical and goal oriented, hence their engagement with extra-medical debates in technical works is often guided by these goals, even when discussing theoretical issues. We can see it very clearly nowadays: no doctor could provide a universally accepted definition of consciousness, yet they are able to diagnose, treat and discuss cases where it is impaired. In antiquity the limits between science and other disciplines were certainly more blurred. However, as we shall see, the authors under discussion tended to orient their reflections towards the practice (that is, towards resolving determined conditions). Even a philosophically informed author such as Galen often used his vast erudition to tweak prestigious thinkers’ ideas in support of his own medical explanations, based on his successful cures. Ultimately, even when discussing issues beyond the strictly medical domain, rather than engaging in pure abstract speculation, the goal of most of these writers’ reflections and theorisations was to find, to justify or to support a certain therapy.

The scope of this book is, therefore, circumscribed to the ‘heuristic role of impaired consciousness’Footnote ¹ within the medical discourse, namely, this condition will be used to understand the way in which the notion of consciousness was conceived by some doctors who tried to reverse such impairment. I will not tackle representations of the concept outside the medical corpus in depth, nor will I discuss how changing ideas about human action, or the evolving relations between men and gods might have impinged upon these doctors’ understanding of consciousness.

In terms of organisation, I propose a dual approach to the material: a longitudinal thematic axis, developed in the course of the three parts in which the book is divided, will illuminate how ideas about impaired consciousness changed and evolved over time. This axis will allow us to contrast continuities and disruptions within each of the three clinical presentations (delirium, sleep and fainting) in the different authors. At all times, in a methodologically self-conscious manner to avoid bias and anachronistic extrapolations, I will make allusions to our current theoretical understanding of these matters.

The transversal axis, on the other hand, follows each group of medical writers (HC, post-Hellenistic authors and Galen) across the different parts of the book, in order to examine issues that are specific for each source (irrespective of their particular take on the main topic under discussion).