By framing sleep as a form of impaired consciousness, a common feature emerged in all the sources, namely, its ambiguous status in relation to various dichotomous oppositions. Indeed, when talking about dormancy, authors seem to be constantly navigating the tensions between health and disease,Footnote ¹ wakefulness and unconsciousness, and in certain cases, even between life and death. Medical writers tended to be torn – to a greater or lesser extent – by some of these oppositions, and they struggled to locate sleep at a determined point between the polar extremes of one or several of these antithetical pairs.

Closely related to the previous finding is another feature that pervades the different periods: the perceived sense of gradual transition between the antithetic extremes, which brings us back to the questions about limits. Whether such extremes are envisaged as a continuous spectrum or as a sequence of discrete stages, the manner in which most of the authors (except for Celsus) discussed sleep points towards ideas of progression, rather than abrupt changes from one state to its opposite. Understandably, if biological processes are gradual, establishing boundaries between intermediate categories is not straightforward, for they have fuzzy edges. When juxtaposing these ancient medical ideas with our existing sociological understandings about sleep,Footnote ² one can see that it is often the social conventions – such as what is acceptable and what is not – that establish clearer boundaries, thereby exemplifying a situation where sociological discourse has an influence over science.

Concerning the terminology, from a historical perspective, there is an evident quantitative shrinkage in the vocabulary of delirium from the Hippocratic authors onwards. The abundant glossaries and attempts at shedding light on the meaning of each termFootnote ³ suggest that those authors had used a larger terminology than their successors to talk about delirium. This reduction might further support the idea of partial synonymy. Ultimately, the Hippocratic corpus was written by many authors from different parts of the Greek world, and it is understandable that they utilised varied terms to talk about similar realities. On the other hand, the fact that the later authors that we looked at required (to describe similar cases) only a few of those terms might indicate that a more limited number of words was sufficient because many of them expressed similar symptoms.

In terms of the organisation and workings of the mind, the previous analysis has yielded other elements that remained constant throughout the different periods and authors, which points towards a general common understanding of impaired consciousness. To be sure, medical writers related the condition to certain abstract notions that they deemed to be compromised (whether we call them the mind, HOFs or a rudimentary idea of consciousness) and struggled to link – in a clear example of tension between theory and clinic – such concepts to the symptoms found in their patients. This becomes particularly evident when considering the extensive use of phrasal terms and their similar structure (a noun head with an HOF and a determiner in the semantic field of ‘damage’ or ‘compromise’). These lexicalisations, therefore, support the hypothesis that an underlying intellectual construct was shared, regardless of the specific nuances that each author gave it (in the case of Galen I have not mentioned any phrasal term, but the underlying constructs are explicitly described).

The tension that emerges from the interaction between these theoretical concepts and the actual clinical findings reflects how these authors – implicitly or explicitly – conceived the relationship between mind and body, cognition and behaviour, thereby characterising the singularity of each medical writer’s understanding. It is, certainly, this tension – which each author resolved in a different manner – that conditioned the changes or evolution in the idea of consciousness discussed throughout the analysis.

Finally, these theoretical constructs also illustrate the important degree of abstract reflection that all these authors reached, which they defended even to the detriment of some observational evidence. Indeed, these rudimentary notions of consciousness – first described with various terms by the Hippocratic texts – were powerful enough to organise most of the later theorisations of delirium, sleep and intermediate states that we have been discussing. Accordingly, the post-Hellenistic authors were happy to sacrifice coherence and consistency in their pathophysiological explanations but preserved these embryonic ideas of consciousness, whereas Galen devised a coherent anatomical and pathophysiological system, but could easily overlook some contemporary nosological classifications in order to preserve these constructs. In other words, the specificities about the way in which each of the authors fragmented or grouped the HOFs – that is, the particularities of each one’s rudimentary notion of consciousness – determined the clinical differences that they were able to see, as well as those that remained obscure.