Heat and Moisture. From the Classification of Fevers to the ‘Truth of Human Nature’

The first part of the essay examines the different premises, of Aristotelian and Galenic origin, for the idea of an inherent consumption of the natural heat of every living body, discussing the contributions of Isaac Israeli, Avicenna and Averroes to the reflection on the relationship between the secondary humours (or moistures) and the peculiar category of fevers called ‘hectic’. The second part of the article discusses how the link between moisture, heat and food was taken up and elaborated by Latin Scholastic masters (in particular Thomas Aquinas), and considers the use of the notion of ‘radical moisture’ in the field of theology. Aquinas does not follow the previous theological tradition, originating with Peter Lombard, which denies the possibility that the matter assimilated through food is part of the bodily core that belongs to every human being from birth. The moisture provided by food is, in fact, inseparable from the (radical) moisture that originally belongs to each individual; as such, it is part of the ‘truth of human nature’ (veritas humanae naturae) that will be restored at the moment of the resurrection of the body.