Galen and Chrysippus on the Soul: Argument and Refutation in the "De placitis," books II-III

One of the intriguing issues in ancient medicine is the controversy over the seat of consciousness, or “command center” (hegemonikon) of the soul. By the fourth century b.c. the leading contenders were the brain and the heart, with physicians and philosophers lining up on either side. In the third century b.c., the Alexandrian anatomists discovered by dissection that the nerves constitute a network independent of the veins and arteries, originating in the brain. Yet not all were convinced: the Stoic philosopher Chrysippus took up the case for the heart as the unitary origin of thought, emotion, and activity—and the debate went on for more than three centuries, until Galen argued strongly and voluminously for the brain. What is surprising is how hard it was for the encephalocentric view to prevail after the discovery of the nerves and their connection to the brain.

Tieleman now sheds a welcome new light on the question by his exhaustive analysis of the relevant text, books II–III of Galen’s On the Doctrines of Hippocrates and Plato, a long work dedicated to showing that Plato (anticipated by Hippocrates) was correct in his view of the soul, with the rational part located in the brain, the spirited part in the heart, and the appetitive part in the liver. Tieleman shows that Galen attempts to combine traditional philosophical concepts and procedures with functional anatomy and scientific proof based on experimentation, arguing the case for the brain from a logical and formal point of view in the scholastic tradition of Aristotle, as modified by recent Platonists. Accepting only demonstrations based on “scientific” premises—defined as ones that pertain to the subject and derive from its attributes—he disqualifies most of the Stoic argumentation, which started from popular opinion, etymology, common language, and statements of poets. Organizing his investigation under the categories of essence and attributes, Galen takes up, in turn, the individual arguments related to each attribute (position, formation, motion, and structure), sorting out those that are relevant and convincing from those that are not. It is in assessing certain individual arguments that experimentation—specifically, vivisection—plays a role, serving as final confirmation of the function of an organ.

Tieleman’s analysis of Galen’s argument illuminates the complex interaction between philosophy and science in antiquity. This debate was not over a mere “fact,” but over scientific methodology and the foundations of philosophy and ethics, cutting to the core of the rivalry between the two dominant philosophies of the era. It reminds us that there were no commonly accepted scientific premises or methodology in antiquity; scientists had to argue their methodology and premises along with their conclusions.

In the second half of the book Tieleman attempts to reconstruct the argument of Galen’s chief opponent. He makes a monumental advance in understanding the argument of Chrysippus’s On the Soul by taking account of Galen’s systematic distortion of it, rooted in his own methodology. He makes a plausible case that Chrysippus framed his argument to counter the Academic skeptics, who denied the possibility of any knowledge of such nonobservable entities as a psychic command center. He argues that Chrysippus offered a sophisticated procedure of progressive clarification and articulation of admittedly unclear evidence, such as might lay claim to the certainty that the Stoics sought. Tieleman thus sheds important new light on Chrysippus’s epistemology and the Hellenistic battle between dogmatism and skepticism.

This book does not make light reading, but it is packed with thoughtful analyses of important texts and issues. It will repay careful study by anyone interested in the methodology of ancient medicine, or in the complexities of Hellenistic psychology and epistemology.