Thomas Aquinas
Thomas Aquinas (1225–1274) was an Italian Dominican theologian and philosopher whose systematic integration of Aristotelian natural philosophy with Christian theology shaped the intellectual foundations of European university medicine for two centuries. He did not write medicine, but his work made natural philosophy academically respectable, defined the physician’s relationship to philosophy, established that urban authorities owed medical care to their citizens, and provided moral theology with the double-effect principle that Catholic medical ethics still applies. His commentary on Aristotle’s De Sensu et Sensato (1269) produced the most cited medieval definition of the physician: the artifex factivus sanitatis, the maker of health. One modern scholar writes that without Avicennian philosophy Aquinas’s theology is “as unthinkable as his philosophy.”(Gutas, 2016)
Life and Context
Aquinas was born into a minor noble family in the Kingdom of Sicily and educated first at the Benedictine monastery of Monte Cassino and then at the University of Naples — one of the first universities established by secular authority, under Frederick II. There he encountered both the new Aristotle and the mendicant orders. His entry into the Dominicans was strongly opposed by his family; the order eventually prevailed, and he went to study under Albert the Great in Cologne and then Paris. He spent most of his career between Paris and Naples, dying at age forty-nine. The institutional context matters: Aquinas lived and worked during the period when the full Aristotelian corpus was entering the European university and generating intense theological controversy.
The Dominicans, Aristotle, and the Natural World
The Dominican order in which Aquinas trained had an institutional investment in Aristotelian natural philosophy. The Dominicans were established to combat the Cathar heresy in Languedoc, and they found that Aristotle’s teleological view of nature — that the natural world is oriented toward purpose and is intrinsically good — offered the best philosophical counter to Catharist dualism, which held the material world to be evil.(French, 2003) Aristotle’s physics could demonstrate that the natural world was good in the realization of potential. The Dominicans therefore spread Aristotelian teaching systematically through the universities, and Aquinas became the order’s most ambitious expositor.
He also absorbed Avicenna deeply. Gutas characterizes Avicenna as the major individual figure in Islamic philosophy, as significant in the East as Aquinas was in the West — an explicit comparative pairing that underscores the structural symmetry between the two systems.(Gutas, 2016) Gutas documents that Aquinas incorporated the Avicennian concept of God as Necessary Being directly into one of his five proofs for God’s existence in the Summa Theologiae, and that in De Ente et Essentia he follows Avicenna’s essence-existence distinction throughout.(Gutas, 2016) Catholic scholars examining the relationship have concluded that Aquinas was far more indebted to Avicenna than previously recognized. Saad and Said write that Averroes’s commentaries on Aristotle “eventually became a key component of the studies of the young Thomas Aquinas,” and that through Aquinas Arab philosophy established a firm foothold in the Western Christian tradition.(Saad Said, 2011)
Aristotelian Naturalism and the Body
Aquinas’s philosophical contribution to medicine was not anatomical or clinical but structural: he legitimized the study of the natural body within a theological framework. By arguing that natural philosophy serves as a handmaiden to theology rather than threatening it, he effectively gave Aristotelian natural philosophy — and thereby Galenic medicine, which rested on Aristotelian foundations — a secure place in the university curriculum.(Peter Dear, 2001)
Jacquart and Thomasset document that Aquinas posited a special intermediate blood, distinct from both menstrual blood and male semen, as the material substance of the embryo.(Danielle Jacquart and Claude Thomasset, 1988) This allowed him to hold that the Virgin Mary’s body supplied pure material for the incarnation while maintaining the Aristotelian account of form and matter in generation.(Danielle Jacquart and Claude Thomasset, 1988)
Medicine in the Scholastic Framework
Aquinas’s most direct contribution to medical thinking came in his 1269 commentary on Aristotle’s De Sensu et Sensato, where he defined the physician to his students as the artifex factivus sanitatis — the maker of health.(García-Ballester, Luis, 2002) Garcia-Ballester notes that this arose in the context of explaining the relationship between natural philosophy and medicine, a question that preoccupied medieval scholars from the twelfth through the fourteenth centuries.
Aquinas drew the boundary clearly: “It is the task of the natural philosopher to investigate the primary and universal principles that govern health and illness; it is the physician’s to put these principles into practice, in keeping with the idea that he is the maker of health. The physician should not limit himself to making use of medicines, but he should also be able to reflect upon the causes of health and illness. To this purpose, the good physician begins his training with the study of natural philosophy.”(García-Ballester, Luis, 2002) This formulation gave the physician a defined but subordinate role relative to the philosopher — the physician applies what philosophy establishes — and simultaneously required that good physicians receive philosophical training. Porter confirms that medieval medical education was shaped directly by “the new Aristotelianism associated with Thomas Aquinas” and that this framing set the academic justification of a medical education as the acquisition of rational knowledge (scientia) within a natural-philosophical framework.(Porter, 1997)
The Canon of Avicenna gained its final academic confirmation in this period partly through Aquinas’s influence. Garcia-Ballester observes that although the Canon had circulated in Latin translation since the 1180s, it did not achieve the dominance it later held until Aquinas’s commentary of the late 1260s effectively ratified the Aristotelian-Avicennian synthesis it represented.(García-Ballester, Luis, 2002)
Medical Ethics and Moral Theology
Aquinas contributed to medical ethics through two distinct channels: direct analysis of the physician’s social role, and moral theology that Catholic medical practitioners applied to clinical decisions.
On the physician’s fee, Thomas Aquinas (1272) classified medical practice as mercenary (mercenaria) in that the physician offers technical knowledge for money, but held that charging for medical services was as much part of the medical function as being technically qualified. Free treatment was justified only for the poor, as an act of charity, not as a general obligation.(Wear_ed, 1993)
On public health, Aquinas’s commentaries on Aristotle’s Politics (1272), following Albert the Great’s earlier work, impressed on university circles that “the urban authorities should be particularly concerned about the health of their citizens.” Garcia-Ballester argues this was a genuinely new doctrine: throughout antiquity, medicine remained free from civil oversight, but the Aquinas-era synthesis changed this, establishing civic provision of medicine as a moral obligation of political authority.(Wear_ed, 1993)
On contraception, Aquinas held a less severe view than papal legislation. Jacquart and Thomasset note that neither Albert the Great, Aquinas, Alexander of Hales, nor Richard of Middleton accepted the position in the Decretals that contraception constituted homicide.(Danielle Jacquart and Claude Thomasset, 1988) The gap between the severity of official rulings and the judgment of working theologians is itself historically significant.
Medieval physicians showed great reticence in addressing sexual relations that diverged from religious and moral norms.(Danielle Jacquart and Claude Thomasset, 1988) They considered homosexuality neither an illness nor a defect of temperament.(Danielle Jacquart and Claude Thomasset, 1988) This caution can be attributed to a certain self‑censorship, leading them to omit or avoid discussions of such relations.(Danielle Jacquart and Claude Thomasset, 1988)
The two moral-theological contributions that had the longest reach into modern medical ethics were the doctrine of ordinary and extraordinary means, and the principle of double effect. Jonsen documents that Catholic moral theologians of the fifteenth century developed the “ordinary vs. extraordinary means” distinction for life-prolonging treatment, an argument that still structures end-of-life care debates today.(Jonsen, 2000) More directly, the double-effect principle — that a forbidden act may be permitted if done with good intent, with proportionate cause, and with a harmful outcome that is foreseen but not intended — was “first formulated by Thomas Aquinas as a justification of self-defense.” Catholic moral theologians then applied it to medical interventions such as amputation and sterilization.(Jonsen, 2000)
Temkin cites Aquinas’s dictum that “the purpose of philosophy is not to know what men have thought, but what is the truth of things” as the foundational principle distinguishing philosophy from history — and notes that this means philosophy and history of medicine pursue fundamentally different aims, though they need each other.(Temkin, 1977)
Influence on Medical Education
The Aristotelian-Thomist synthesis was not merely speculative; it structured how physicians were trained. French describes how the new logic — especially the Posterior Analytics — gave doctors a tool for constructing authoritative arguments, and how the Dominican spread of Aristotelianism was central to this process.(French, 2003) Frederick II’s requirement that three years of logic precede five years of medicine was part of the same movement in which Aquinas was the philosophical anchor.
Pellegrino and Thomasma, writing in 1993 on medical virtue ethics, explicitly adopted the “Aristotelian-Thomist” definition of virtue as their framework, arguing that subsequent definitions had not improved on it.(Pellegrino, 1993) Central to this synthesis was Aquinas’s integration of Aristotelian natural virtues with Christian theological virtues, giving special prominence to prudence as the bridge between moral and intellectual virtues — a move that accepted the classical cardinal virtues but enriched them with Revelation.(Pellegrino, 1993) They argued that prudence — Aquinas’s recta ratio agibilium, the right way of acting — is indispensable to clinical judgment, which requires the kind of integration of scientific and moral reasoning that only practical wisdom provides.(Pellegrino, 1993)(Pellegrino, 1993) Aquinas’s enrichment of Aristotle’s phronesis to include supernatural virtues gave medical ethics a broader normative register than the purely naturalistic Greek original. On justice, Aquinas connected it to the theological virtue of charity, giving the social virtues an additional impulse toward altruism absent from classical Greek thought — a step that mattered for the clinical setting where disinterested concern for the patient’s good is required.(Pellegrino, 1993) Pellegrino and Thomasma regard Aquinas’s account of intentionality as “still the richest, most insightful, and most morally relevant”: the virtuous physician must exhibit maximal congruence between interior intention and exterior action, making genuine virtue irreducible to the right performance of external duties.(Pellegrino, 1993) For Pellegrino and Thomasma, the teleological approach — relating virtues to the ends of medicine — was “Aristotelian and Thomistic” in the most direct sense.(Pellegrino, 1993)
See Also
- aristotle
- avicenna
- albert-the-great
- scholastic-medicine
- medical-ethics
- university-medicine
- dominican-order
- double-effect