In a spectacular career rose from gladiator physician in Asia Minor to court physician in the Rome of Marcus Aurelius . The son of a wealthy architect, he enjoyed an excellent education in rhetoric and philosophy in his native town before turning to medicine. After studying medicine further in Smyrna and Alexandria (1) , he began practising in Pergamum in 157, and went to Rome in 162. Driven out by hostile competitors, or fear of the Plague , in 166, he returned in 169, and remained in imperial service until his death. A prodigious polymath, he wrote on subjects as varied as grammar and gout, ethics and eczema, and was highly regarded in his lifetime as a philosopher as well as a doctor.

Although Plato (1) and Hippocrates (2) were his gods, and Aristotle ranked only slightly below them, he was anxious to form his own independent judgements, and his assertive personality pervades all his actions and writings. His knowledge was equally great in theory and practice, and based in part on his own considerable library. Much of our information on earlier medicine derives from his reports alone, and his scholarly delineation of the historical Hippocrates and the writings associated with him formed the basis for subsequent interpretation down to the 20th cent. Large numbers of new texts, some book length, continue to be recovered, mainly in translation, but some in the original Greek.

He made ambitious efforts to encompass the entirety of medicine, deriding those who were mere specialists or who rejected any engagement with theory. The best physician was, whether or not he knew it, also a philosopher, as well as a man good with his hands. Galen reports some spectacular surgical successes, like his removal of a suppurating breastbone, and he expected even moderate healers to be able to perform minor surgery . Although he rarely refrained from laying down the law on how to diagnose and treat patients, he equally stressed the inadequacy of general rules in an individual case. Although contemporaries credited him with almost miraculous skills in prognosis (which incorporated diagnosis), especially in what might be termed stress-related diseases, he replied that they were easily derived from Hippocratic first principles and that a sound diagnosis depended on close observation of every detail. His authoritative bedside manner would also have contributed to his success with patients.

Galen was particularly productive as anatomist and physiologist (see anatomy and physiology ). Dissecting animals, especially monkeys, pigs, sheep, and goats, carefully and often, he collected and corrected the results of earlier generations by experiment, superior factual information, and logic. His physiological research was at times masterly, particularly in his series of experiments ligating or cutting the spinal cord. At others, his reliance largely on non-human anatomy, coupled with his belief that the basic structures of the human body had been described by Hippocrates, led him to ‘see’ things that were not there, e.g. the rete mirabile at the base of the human skull, cotyledons in the womb, and a connection between spleen and stomach.

His pathology , founded on the doctrines of the four humours and of three organic systems, heart, brain, and liver, explained disease mainly as an imbalance, detectable particularly through qualitative changes in the body. His pharmacology and dietetics were largely codifications of earlier learning, enlivened by personal observations and occasional novel ideas, as with his (unfulfilled and later influential) attempt to classify drugs according to twelve grades of activity.

His philosophy was equally eclectic. His major enterprise to create a logic of scientific demonstration, surviving only in fragments, went beyond Aristotle and the Stoics (see stoicism ) in both the range and precision of its arguments. Later authors credited him with innovations in syllogistic logic, and with powerful critiques of Peripatetic and Stoic ideas on motion. In his psychology, he favoured a Platonic tripartite soul over the Stoic unity, bringing the evidence of anatomy to support his case, in the same way as he used Aristotelian ideas on mixture to explain changes in the physical humours. His ‘philosophical autobiography’, On My Own Opinions, reveals the interactions between his medicine and his philosophy, as well as the limits he placed on certitude.

Galen's monotheistic views, his ardent belief in teleology, and his religious attitude—even anatomy was a veneration of God, and he was convinced of the personal protection of Asclepius —foreshadow the Middle Ages. His dominant influence on later generations, comparable only to that of Aristotle, is based on his achievements as scientist, logician, and universal scholar, and on his own self-proclaimed insistence on establishing a medicine that was beyond all sectarianism. The dissension of earlier science could be conquered by an eclectic rationality based ultimately on notions in which all shared, and be turned into a stable system of Galenic medical and practical philosophy. See medicine , § 6. 1.