By AD 650 ancient medicine had taken on the form in which it was to dominate the theory and practice of medicine in the Greek East, and subsequently in the Muslim world and the Latin West, for a millennium - namely, Galenism. Learned doctors and other intellectuals were now agreed that the human body, organised anatomically and physiologically into three almost separate systems based on the brain, heart and liver, depended for its health ultimately on a balance between its four constituent humours, blood, bile, black bile and phlegm. This balance varied according to the individual's age and diet (in the broadest sense of the term), the season of the year and the environment, and determined not only physical but also mental well-being. It was a system standing firmly on the twin pillars of observation and logic, and gained added authority from the longevity of the theories on which it was based and from the ease with which it could be co-ordinated with other systems of thought such as Aristotelianism, Platonism and monotheism. It was not entirely immune to change, although its rhetoric of certainty did not allow for radical developments or more than a circumscribed area of disagreement. Such a theory, backed up by centuries of observations and apparently effective therapies, had deservedly triumphed. The vigorous debates of fifth-century BC Greece or second-century Rome were long gone: arguments over the interpretation of Galen had replaced disputes over alternatives to Galen. 1 How the pluralism of earlier medicine developed into this near-monolithic system and how it interacted with an increasingly desecularised world are the main themes of this chapter.
Any answer to the first question runs into an immediate difficulty. The century and a half that follows the death of Galen is a black hole in the history of medicine. No completely surviving text can be assigned with confidence to this period, except for Gargilius Martialis' book on Medicines from Fruits and Vegetables and a strongly Neoplatonist essay, preserved under the name of Galen, on the way in which the foetus receives its soul. 2 Several recipes for both animals and humans, as well as magical tricks and useful hints on everything from archery to surveying, were included by the Greek writer Julius Africanus in his Tapestries (Cestoi), written in the 220s. 3 A few scattered fragments of veterinary authors such as Theomnestus, writing around 326, and his slightly