Galen (d. c. 210), the most influential of classical medical writers, modified the Aristotelian framework and fitted it to the doctor’s practical concern for bodily alteration. Galen subdivided Aristotle’s most dynamic category, efficient cause, into three medical causes: a body’s predisposition (in medieval Latin, the causa antecedens); the external factor leading to a harmful change in the body (causa primitiva or procatarctica); and the condition actually preventing the body’s proper function (causa coniuncta or contentiva).9 Later medical writers did not always employ this exact vocabulary, but their nosology tended to address all three topics in their discussions of causes. Yet the most popular and widely elaborated framework of specifically medical causation was the triad of categories known as the res naturales, the res non naturales, and the res contra natura, or, in a Middle English translation of Guy de Chauliac’s inventarium—“kyndely thinges and noght kyndely and thinges agenst kynde.”10 These were popularized in the Isagoge of Joannitius (Hunayn ibn Ishaq, d. 873), which was translated by Constantine the African (d. c. 1098). The res naturales encompassed what was intrinsic to the body; the contra-naturals consisted of diseases and their symptoms, which opposed the body’s health; and the non-naturals stood in between. Neither good nor bad in themselves, the non-naturals were those elements of everyday life—air, diet, exertion, rest, excretion, and mood—that influenced somatic states. As Galen remarked of the six factors, “The body cannot but be altered and changed in relation to all these causes.”11 The highest expression of the medieval physician’s art was thought to be the management of these non-naturals. English readers’ interest in their proper handling is evident in the popularity of texts mixing medical and moral advice, like John Lydgate’s most copied poem, the “Dietary” (discussed below), and recensions of the advice-for-princes manual the Secretum Secretorum, which included instructions on hygiene and regimen.
Even with these three flexible etiological schemata, medical writers in the late thirteenth century seized on a further causal rubric, that of “specific” or “occult” causation. It accounted for effects that could not be predicted in advance on the basis of primary qualities. For instance, no calculation of degrees of heat and cold, dryness and moisture could foretell the behavior of a magnet. Its properties of attraction could only be discovered empirically—although once discovered they were considered natural, not magical or supernatural. “Occult causation” made room for what could be learned from experience, beyond existent medical theory.12
These several schemes of etiological thinking—Aristotelian, Galenic, Joannitian, and (as an auxiliary) “specific” or “occult”—were products of learned medicine’s etiological imagination. They show the science’s restive puzzling over how to understand the nature of living bodies and the changes they undergo. Yet despite these many tools—or, in some cases, because of them—etiological explanation in phisik remained difficult. Causation cannot simply be observed. It is a relation that requires abstract thought to formulate. Medical experts needed to posit connections among causes, symptoms, and treatments. The intricacy of the task became an increasingly common topic of discussion in medical writing. For instance, the French surgeon Henri de Mondeville (d. 1316) drew attention to it in his Chirurgia of the early fourteenth century, which subsequently circulated in England.13 According to Mondeville, it is only in the case of such thumpingly obvious causes as “a stick, or stone, a knife, or something of that kind” that ordinary people can perceive relationships of causation. When the harm results rather from “an intrinsic, interior, or antecedent cause [a causa intrinseca interiore vel antecedente],” the vulgus is at a loss.14 Mondeville, like Lanfranc of Milan, was part of a tradition that aimed to intellectualize surgery, and causal explanation was central to that project. His written expertise is laid out on the page like academic commentary: “I have presented the appropriate surgical procedure pure and simple, but next to it I have presented its causes and reasons and explanations in smaller letters than the text itself, as if in a commentary or gloss.”15 The manuscript layout insists on the connection between surgical practice and causal explanation. As he goes on, Mondeville declares that a practitioner who fails to realize that every illness derives from a general and rational system of causes will, as a result of this ignorance, attribute each sickness to an isolated cause and will therefore be no better than an empiric.16
Mondeville was an especially innovative medical thinker, and one of the points where he can be seen responding to the intellectual problems of the early fourteenth century is in his unusual enumeration of fifty-two contingentia, or contingent factors, in his surgical practica.17 The list begins with the familiar Joannitian framework of naturals, non-naturals, and contra-naturals and then broadens to include miscellaneous factors not captured under any formal systemization of medical causes. Mondeville explains that the surgeon usually needs to know everything, omitting nothing, about all the details of a patient’s past that may bear on his choice of treatment.18 Each of these factors—“every individual condition as revealed in a patient, or in a wounded member, or in an illness, or wherever, whether it be favorable or harmful [omnis particularis conditio existens aut reperta in patiente, membro laeso et morbo curando et aliis aliquibus inferius hic notandis, quae condicio nocet aut confert]”—“creates a problem for the surgeon during treatment [ponit difficultatem in curatione morbi curandi per cyrurgicos].”19 Mondeville’s list of contingentia insists that in applying general scientific principles to particular cases, the surgeon has to be constantly alert to individuating factors.20
The difficulty of etiology found its paradigmatic expression in what was the most well-known piece of medical writing in the Middle Ages, the first aphorism of Hippocrates: “Life is short, art is truly long; the time is acute, experience treacherous, and judgment difficult” (Vita brevis, ars vero longa; tempus autem acutum, experimentum fallax, iudicium autem difficile).21 Or, in the paraphrase most familiar to students of Middle English literature: “The lyf so short, the craft so long to lerne, / Th’assay so hard, so sharp the conquerynge.”22 While the narrator of Chaucer’s Parliament of Fowls deploys the aphorism to comment on the labors of love, and indirectly, the labors of poetry, the phrase’s first context of meaning was medicine. The latter half of the aphorism continues: “The physician must not only be prepared to do what is right himself, but also to ensure that the patient, the attendants, and the externals cooperate.”23 From its earliest versions, the articella (the collection of texts that served as the basis of academic medical education from the twelfth century to the end of the Middle Ages) included the Aphorisms alongside Galen’s commentary on the same text. Galen directly links the meaning of the first aphorism to the ambiguities of causation: “If someone is treated with different medicines, and improves or worsens as a result, it is not easy to decide which of these helped or harmed him.”24 The first medieval expositors of the aphorism emphasized the difficulty resulting from both the numerousness of physical influences and the vastness of medical learning. Bartholomew of Salerno explains, “Art is long because of the multitude and difficulty of things comprehended in the art” (ars vero longa propter multitudinem et rerum difficultatem huic arti subiacentium), and Maurus of Salerno identified medicine’s “length” with its dispersion into a multiplicity of rules and precepts (Ars est longa, idest variis regulis et preceptis diffusa).25
In 1301 Arnau of Vilanova (d. 1311), then perhaps the most famous physician in Europe, delivered a set of lectures to medical students at Montpellier concerning this single Hippocratic aphorism.26 In the first lectio Arnau describes the factors that make the acquisition of medical art a project that