After looking at delirium – mostly from the hyperactive end of the spectrum of consciousness – in this part I shall explore the hypoactive end, particularly sleep. This second ideal exemplar, which is a universal process, intrinsic to human existence, also presents challenges in terms of boundaries. Just as the fuzzy edges between delirium and mental illness enabled us to reflect upon the chronological changes in the notion of disease, the analysis of sleep will help us deepen our inquiry into the blurry boundaries between health and illness. Additionally, questioning the terminology used to describe alterations at both ends of the spectrum of consciousness and their recovery will be useful in understanding some of these doctors’ ideas about the mind.

Sleep has often been construed as a vaguely defined territory with fuzzy edges, in the midst of apparently contradictory tensions: beyond the difficulty in establishing when it should be regarded as a normal physiological process and when as a sign of disease, the boundaries that separate it from drowsiness and hypoactive wakeful impaired consciousness, on the one hand, and from total loss of consciousness, on the other, are rather blurry.Footnote ¹ In other words, even the apparently self-evident contrast between wakefulness and sleep can be tricky. To quote Williams, sleep ‘furnishes us with a sense of what it means to be conscious, just as consciousness furnishes us with a sense of what it means to be asleep’.Footnote ²

To address these ambiguities – not always resolved by the medical texts – apart from the biological approach I will consider in my analysis some recent contributions by other disciplines, which have also explored the phenomenon and engaged in similar debates. Sleep is becoming an increasingly important field of research among sociologists and anthropologists, whose perspectives often illuminate relevant areas that medicine leaves in the dark.

In a pioneering paper, Taylor proposed to study sleep as a social rather than a biological phenomenon. He suggested that only physiology and medicine had addressed the topic so far, and their questions were only aimed at the ‘whats’ and ‘whys’. He claimed, instead, that there were still important inquiries to be made concerning its sociological dimensions, such as ‘How? When? Where? With whom? and What meanings can be attributed to sleeping?’Footnote ³ Considering that scientific ideas are often entangled with sociological beliefs, and medical concepts can be influenced by extra-medical realities, asking such questions about ancient societies can provide us with important information.

Not far from these approaches, Oberhelman offered a more anthropological take to the matter. He highlighted how sleeping, due to its inseparable link with dreaming, pervades various discourses on disease and healing in antiquity. Not only was it conceived as a symptom of disease, as part of a healthy regimen and as the treatment for certain illnesses, it also appears as a component of rituals under the form of incubation in temples, and is even associated with death in epic poems.Footnote ⁴

In other words, in order to explore the different ancient medical writers’ perceptions of sleep and their link to reduced/impaired consciousness – or unconsciousness – my analysis will place the phenomenon against a background of sociological and anthropological realities.Footnote ⁵ Such backgrounds will both inform the medical discourse and help us to define the fuzzy contours of sleep. Undoubtedly, the tensions wakefulness–sleep and health–disease confer a liminal status to this clinical presentation.Footnote ⁶ Furthermore, they illuminate the peripheries of sleep; namely, the areas where the discourse on sleep intersects with other forms of impaired consciousness, thereby illuminating the extent to which authors understood them to be related or easily confusable conditions.

Additionally, this prototypical presentation enables us to explore how the authors construed different depths of sleep. As described in Chapter 1, the cognitive model of classification based on ideal exemplars (chosen to define impaired consciousness) allows membership gradience. When applying this idea to sleep, one could argue that the degree of identification of any description with this prototype is inversely proportional to the level of consciousness that the author is trying to convey: the deeper a person sleeps (that is, the closer to the ideal archetype of sleep), the lower his level of consciousness. Conversely, as sleep wanes into drowsiness, the features become increasingly distant from that ideal exemplar, and accordingly, the level of consciousness increases.

Finally, this clinical presentation can also illustrate – when focusing on the terminology utilised to describe its hyper- and hypoactive peripheries – the idea of mind underlying the accounts of sleep and delirium. Accordingly, the analysis will show how the different sources perceived, described and organised the HOFs that were damaged during episodes of impaired consciousness, and how they subsumed some or many of these mental capacities within notions akin to our idea of consciousness, thereby suggesting that they had an embryonic or rudimentary intuition of this concept.