Galen (AD 129–c.210)

Galen was the most influential doctor of late Greco-Roman antiquity. But he was also a notable philosopher, who desired to effect a synthesis of what was best in the work of his predecessors, not only in medicine but also in logic, epistemology, philosophical psychology and the philosophy of science and explanation. In logic he made use of both Aristotelian and Stoic material, but supplemented them with his own treatment of relational logic. His epistemology, while resolutely anti-sceptical on the grounds that nature could not have furnished us with systematically delusive sense-organs, was none the less sober and cautious: some philosophers’ questions are simply unanswerable. He attacked the Stoics’ unitary psychology, establishing by means of detailed experiments that the brain was the source of voluntary action. Finally, drawing on the philosophical and medical tradition, he crafted a theory of cause and explanation sophisticated enough to rebut the sceptical challenges to such notions, and rich enough to enable him to construct a comprehensive physiology and pathology on its basis.