Theories on pneuma in the work of the late Byzantine physician John Zacharias Aktouarios

This chapter offers the first critical examination of On the Activities and Affections of the Psychic Pneuma and the Corresponding Regimen, written by the late Byzantine practising physician John Zacharias Aktouarios (ca. 1275–ca. 1330). It shows that John identified four distinct pneumata and introduced an innovative theory in which each of the four pneumata is correlated with two primary qualities (unnamed, ‘gastric’ pneuma: cold and moist; naturalpneuma: warm and moist; vital pneuma: warm and dry; psychic pneuma: cold and dry). Ultimately, he made a direct connection between the quality of pneuma and one’s daily regimen, including diet, physical exercise, bathing, and sleep, thus providing a systematic introduction of the qualitative change in pneuma as an object of treatment.