Contemporary medicine conceives total loss of consciousness as a global alteration of brain activity. It can have a neurological origin such as in seizures, strokes, head trauma or other aetiologies that ultimately affect the central nervous system (intoxications, infections, liver conditions, etc., where the damage is mediated by substances that compromise neurons). Alternatively, total loss of consciousness can be caused by impaired cerebral blood flow. Such cases can be the result of significant haemorrhages; but they can also be transient and self-limited episodes, which we define as ‘syncope’Footnote ¹ or, less technically, swoons and fainting. The latter are usually preceded by dizziness, light-headedness and sometimes visual and auditory disturbances (pre-syncope). Three main varieties of syncopes are usually recognised: those that are neurally mediated (or vasovagal), which are due to a transient impairment of the autonomic nervous system; postural (or orthostatic) hypotension, in which the blood pressure drops when individuals stand up (and hence they faint), owing to a permanent disorder in the autonomic nervous system; and finally, cardiac syncope, secondary to arrhythmia or a structural heart disease (mainly valvulopathy or ischaemia). In contemporary times vasovagal syncopes are epidemiologically the most frequent and are typically triggered by strong emotions, pain and – often – the sight of blood. Accompanying signs can include pallor, sweating (diaphoresis), cardiac symptoms (especially palpitations), gastric symptoms (such as nausea and vomiting), hypoventilation and sudden muscle contractions (myoclonus). These episodes are sometimes described as near-death experiences.Footnote ² This chapter analyses the way in which ancient doctors explained and treated these kinds of conditions.

In order to talk about total loss of consciousness, compounds of psuchê have often been used in the ancient Greek medical tradition, and compounds of anima in Latin. As we shall see, there is a distinction among most ancient medical writers (in some it is more subtle than in others) between two forms of this prototypical presentation: firstly, one that authors perceived to be related to the soul; and secondly, one framed as an eminently physical condition, where bodily symptoms predominated.

The discussion, therefore, will address what Helen King has denominated as ‘common to body and soul’. The tension between these two elements constituted a central topic of debate among philosophers in antiquity in terms of what pertained to the body, what to the soul and what was shared by both.Footnote ³ Closely related to this discussion is the debate concerning the authors’ support for either instrumentalism or materialism (the former being the idea of the body as simply an instrument of the soul, and the latter as the soul depending completely on the effect of bodily substances).Footnote ⁴ The above-mentioned two forms of understanding of total loss of consciousness will allow us to explore the extent to which medical writers engaged in these controversies, and how they negotiated between these opposite extremes.

In other words, the complete disruption of HOFs that occurred when a patient fainted – where wakefulness, cognition, perception and movement (that is, alertness, connectedness, responsiveness) were temporarily suppressed – can provide some clues about notions held by these medical writers, which went well beyond their ideas around consciousness. Indeed, implicit in those explanations are their perceptions concerning the soul, its relation to the body and occasionally, even their views on the boundaries between life and death.

It should be emphasised, however, that in no way does the following analysis pretend to be an exhaustive philosophical study on ancient psychology. As stated in the Preface, it will only address the notion of the soul as far as it is relevant to understanding these medical writers’ stances on impaired consciousness and it will only touch upon extra-medical sources (mainly philosophical) whenever they are key to illuminating some of these authors’ claims.