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Philosophy Then

The Best Doctor is Also a Philosopher

Peter Adamson on medicine in the ancient world.

One of the most familiar truisms about the history of philosophy is that in previous ages, the word ‘philosophy’ had a broader meaning than it does today. And like any good truism, this one is actually true. Until relatively recently, researchers we would now call ‘scientists’ were called ‘natural philosophers’ or simply ‘philosophers’. This usage goes back all the way to the roots of philosophy in Europe, with the Presocratics, whose ideas concerned science at least as much as the topics we now teach in philosophy classes. The man typically credited with being the very first philosopher, Thales of Miletus, is reputed to have been an expert in astronomy, and to have made a killing on the olive oil market by renting all the olive presses after he was able to predict a bumper crop.

But the real hero, when it comes to integrating science with philosophy, was Aristotle. We usually think of him as a pioneer in fields like metaphysics, logic, and ethics – another truism that is perfectly true. But he also pretty well invented biology, writing extensive zoological works that cover everything from embryology to the bitter feud that rages between the eagle and the nuthatch. Aristotle’s associate, the less famous Theophrastus, continued the research program by writing works on minerals and plants. All this called for serious, detailed empirical observation. Aristotle was not afraid to get his hands dirty, quite literally: he engaged in such pursuits as the dissection of sea creatures. As a result, while Aristotle’s views on cosmology and the soul now strike many as antiquated, in every sense of the word, his observations about the natural world often stand up to scrutiny. (Not always: at one point, he dismisses as evidently false the notion that light takes time to travel from one place to another).

One animal that Aristotle did not dissect was the human being. Taboo trumped curiosity, and anatomy in the ancient world was at first restricted to the study of animal bodies. This changed in the third century BC, when two anatomists at Alexandria, named Herophilus and Erasistratus, supposedly went so far as to dissect even living humans, taking criminals as their unwilling subjects. Gruesome stuff. But it helped these doctors to make a momentous discovery, by distinguishing the nervous system from the blood vessels. Centuries later came the most influential figure in the history of pre-modern medicine, Galen. He’s the author for whom we have the largest surviving Greek corpus, because his works were so avidly read, and hence copied into many manuscripts, in the following centuries (if you still aren’t impressed, he was also Marcus Aurelius’s doctor). Galen didn’t dissect humans, but he was a master anatomist who even put on public displays involving vivisection of animals.

What, if anything, does all this have to do with philosophy as we understand it today? Quite a lot, as it turns out. Though some ancient doctors based their practice on nothing other than guidelines taken from experience, others based treatments on a theoretical understanding of the human body. This is where famous doctrines like the four humor theory come in. While Galen emphasized the importance of experience, he also made a significant role for theory in his medical writings. To see the implications, one need only mention the title of his work That the Best Doctor is Also a Philosopher. For Galen, a medical expert cannot afford to be ignorant of ‘natural philosophy’. One must understand, for instance, that complex bodies are built up out of the four elements, and that organic bodies have parts with innate functions.

These two points are common ground between Galen and that scientific pioneer, Aristotle. But Galen also clashed with Aristotle, notably over a question that has both philosophical and anatomical aspects: which part of the body houses the ‘ruling faculty’ (hegemonikon) that controls the whole animal? Aristotle, and also Galen’s favorite opponents the Stoics, thought this faculty was seated in the heart. Claiming solidarity with Plato and Hippocrates, Galen instead put it in the brain. And thanks to his skill as an anatomist, this became one of the first cases in history where a philosophical debate was settled empirically. Galen performed dissections to show that parts of an animal body can be incapacitated by cutting nerves stemming from the brain. An especially persuasive use of this method, Galen remarked, is to render a pig suddenly mute, since the interruption of its terrified squeals is so striking.

Because Galen became the indispensable authority for later medical writers, and because many of these writers were also philosophers, medicine and philosophy continued to be closely intertwined. The point applies to famous European thinkers such as Descartes. But it was never more crucial than in the Islamic world: a short roll call of thinkers who wrote on both medicine and philosophy would include al-Farabi, al-Razi, Avicenna, Averroes, and the Jewish thinker Maimonides. Galen’s influence makes itself felt in their ideas about knowledge (that mix of experience and theory), anthropology, and even ethics, with moral instruction being understood as a kind of medicine that applies to the soul instead of the body. Just as bodily health consisted in a balance of humors, so virtue consisted in an appropriate balance between psychological forces: the illness of melancholy was caused by an excess of black bile, the psychic malady of greed by an excess of desire. Admittedly, medicine was usually seen as a discipline allied to philosophy, rather than as an actual part of philosophy. Yet Galen’s heirs were prepared to believe, not only that the best doctor is also a philosopher, but also that the best philosopher is also a doctor.

Peter Adamson is the author of A History of Philosophy Without Any Gaps, Vols 1 & 2, available from OUP. Both are based on his popular History of Philosophy podcast.