I am continuing my commentary of the excellent Cambridge Companion to the Stoics, of which I have published a number of installments already (e.g., here, here, here, here, and here). I’ve got to the chapter by R.J. Hankinson, on “Stoicism and medicine.” And no, this isn’t going to be a post directing you to use some kind of Greco-Roman “alternative” treatments for your cold.
Hankinson begins by noting that some ancient philosophers were actively interested in medicine (e.g., Sextus Empiricus), and vice versa a number of physicians had interesting things to say about philosophy (most obviously Galen). More broadly, their discussions really went to the core of the issue of the nature of science and the limits of epistemology — in many ways a very modern issue.
One big debate at the time concerned the location of the “soul,” or more specifically of the reasoning function. Setting aside the obviously non-materialistic take of Plato, Aristotle suggested that sensation and thought were located in the heart, a position later endorsed by the Stoics. Yes, I know, this sounds ridiculous, but early anatomical research had clearly shown the heart to be an important center of the body, from which all sorts of major and minor ramifications spread throughout the organism, so the heart-centered hypothesis wasn’t that crazy (and it was based on empirical studies, unlike Plato’s metaphysics).
However, already Alcmaeon of Croton (~480BCE) had identified the brain as the organ of reason, and shortly thereafter other authors also considered it the location of pleasure and emotion.
Part of the confusion, and of the reason why the Stoics initially sided with the heart theory, was that Praxagoras thought that the nerves were the end-points of the arteries. However, soon Herophilus not only differentiated the nervous systems from other structures, but was even able to distinguish between motor and sensory nerves.
Chrysippus, the third head of the Stoa, either did not know of Herophilus’ work, or did not think it valid, which is why he sided with the heart theory, earning Galen’s scorn.
Nonetheless, the Stoics did have some interesting insight. For instance, they thought that what they called “pneuma” was a fundamental substance that permeated the world and which comes in three types, one of which made both animal perception and human thought possible. While the details are sketchy, Hankinson says: “the role of pneuma as an analogue to the function of the motor nervous system is clear.”
I find Hankinson’s discussion of causality and determinism in this chapter particularly interesting. Here Galen and Chrysippus find themselves roughly on the same side, and against non-Stoic authors like Alexander of Aphrodisias.
At issue is Alexander’s contention that if the Stoics are right and the universe is deterministic, then we cannot possibly be held responsible for our actions. This, obviously, is a very modern discussion, currently being played out between determinist incompatibilists and compatibilists about free will. Here is how Hankinson’s summarizes the Stoic position:
“Fate, properly so-called, is not to be identified with the whole causal structure of everything, but rather only with the initiating causes of processes or actions, the external stimuli which set them going. … To take a particular example of the sort relevant to the discussion of freedom and responsibility, the stimulus to my seeking food may be a sense impression of something edible; but my merely seeing it is not enough to make me eat – a whole internal structure of beliefs, desires, and volitions is called into play as well. More importantly, the same stimulus may affect different people differently: oysters move me to gluttonous excess while leaving you cold. The proper explanation of this discrepancy … is to be found in the differences in our internal dispositions. I am responsible for what I do, even though it is caused, because it is my dispositions and beliefs that are doing the crucial work in producing the outcome. Neither the fact that they would not have done so without the stimulus, nor the fact that, given the stimulus, they cannot (other things being equal) fail to produce the outcome, are relevant.”
I think this is a pretty darn sophisticated account of compatibilism. I’m equally confident that it will leave incompatibilists unmoved, just as it did in the time of Chrysippus.
The broader discourse, however, as I mentioned at the beginning, was about the limits of epistemology and the nature of science. Here Galen strikes a better compromise than the Stoics: he maintained that no physician could be good at medicine if he didn’t take into account philosophy (in this he was reacting to a group of empiricists who wanted nothing to do with metaphysics); but he also faulted the Stoics, among others, for not paying sufficient attention to the empirical advances being made by the science of anatomy even at the time. Later Stoics agreed, and ended up belatedly endorsing the brain theory of thought over the now increasingly untenable heart theory.