Flesh in the Age of Reason by Roy Porter

accommodated and even required it. Responsible for purposive functions and movement, animal spirits were central to Galenic medicine – and thence to subsequent European philosophizings about life for the next millennium and a half. After all, for the soul to act on the flesh, was there not an evident need for bridging media, partaking of the properties of both? Spirits formed precisely those intermediaries. Even when the rational soul was not consciously in charge, spirit represented the vivifying element present, for instance, in the digestive juices or in semen, imparting to them their vigour. Such spirits drew their potency, many thought, from an aerial substance in the atmosphere, the
pneuma
, or divine spirit, breathed into the lungs.
    In all such formulations, ‘spirit’ conveys subtly nuanced shades of meaning: not all ‘spirit’ was what we would today call ‘spiritual’. One meaning pertains to the purely immaterial, as, with the coming of Christianity, the Holy Ghost or Holy Spirit – a spirit which presupposes a difference in kind (the ‘spiritual’) from things gross, concrete or fleshly. But ‘spirit’ chiefly conveyed the idea of an exceedingly fine medium, the most ethereal possible, far more delicate than the ponderous substance which ‘matter’ might routinely suggest. The value of the term ‘spirit’ in traditional biomedical discourse lay in this very flexibility.
    Galenic medicine identified an innate spirit (
spiritus insitus
) which pervaded all parts of the body, approximately the equivalent of ‘life’ in the most general sense. It found expression in the body’s ‘innate heat’ and ‘primitive moisture’: without these, there could be no animation. These were what differentiated the living from the inanimate. In addition to this general innate spirit, specific spirits were elaborated – the natural, the vital and the animal. These were superfine in character and relatively localized, being produced in and by specific organs, namely, the liver, the heart and the brain respectively. Each played a special physiological role.
    Dominant Galenism also assimilated the Aristotelian doctrine that objects consisted of form and matter. Matter was a potential which could be actualized by form – for instance, wood could be ‘in-formed’ into a branch or a table. Matter was thus indeterminate, inchoate, rather low-grade stuff, awaiting the form which articulated and enhanced it; but it was also the ‘principle of individuation’ – what made things particular or unique. Tables were universal in their (Aristotelian) form or (Platonic) Idea – every table had legs and a top, and was for putting things on; but it was the particular type and piece of timber which made this or that table distinctive – which gave it its ‘quiddity’, its dimensions (or quantity), grain and shade. Qualities or virtues, in other words, were those powers possessed by forms which made them capable of bringing about change in matter. The form of man was the soul, and the soul was the form of the body. In Aristotelian and Galenic thinking, dynamic activity depended on the form; the soul was thus the mover and end (final cause) of all the actions of living bodies (not just humans).
    A human being was thus represented in traditional biomedicine as a complex, differentiated but integrated whole (the Platonic or Christian immortal soul, as we have seen, brought additional complications). The humours formed one facet, and their disposition was reflected in the ‘complexion’ (or outward appearance) and the ‘temperament’ – or, as we might say, personality. Humours, complexion and temperament constituted an interactive system, equipped with feedback loops.
    Within this framework, illness was standardly read not as a random assault from outside, but as a significant life-event, integral to the sufferer’s whole being, spiritual, moral and physical, to his or her humoral balance, and to his or her