§6. Prince of Ancient Physicians

Physicians were sensitive in a way philosophers typically were not to the limits of knowledge (the ancient skeptics are an obvious exception, though they too were affiliated with medicine), and were interested, more than the philosophers ever were, in methods of inquiry.

Galen refuses to ally himself with any medical sect or philosophical school. The best sect is unstinting dedication to the truth. He understands the question dividing empiricists and rationalists to be whether experience alone is adequate for a doctor, or whether reason contributes to the medical art. He comes down in favor of a qualified empiricism. He repeatedly insists on one absolute body of medical knowledge that rests entirely on experience. He says of his work Outlines of Empiricism, “I have written this book to show how it is possible that somebody should acquire the art of medicine by expe­rience without the use of reason [i.e., theory]”⁴⁷

Experience does not mean perception, or not merely that.

By “trial and error alone,” he says, relying on nothing but experience, people “could become good doctors in the Empirical tradition” But they would not be perfect doctors. They would not have method, or complete method, and could not offer scientific demonstrations. Galen says that “the entire therapeutic method is independent of experience” being founded on indications; “for everything that is distinct from experience is called indi­cation (endeixis)” As this suggests, Galen’s method goes beyond Aristotle, especially in the interest of discovery. Eyes and ears and other sense organs supply indispensable supplementary axioms. “I reach my conclusions on the things which I shall use for treatment of the disease by inference from those invisible matters which I discovered with the help of those perceptible to the eye” The science in medicine requires some propositions that can only be known by observation. For example, “Unforced inhalation is produced by a different set of organs and muscles and nerves from those which produce forced inhalation” No deduction from universal principles will tell you that, yet want of it stymies a scientific understanding of respiration.⁴⁹

Some axioms are grasped by thought alone, and others given with sense perception, though that does not make them inductions, which Galen dismisses as bootless.

The rationalist reply to criticism by medical empiricists is, first, that there is no such thing as empirical knowledge—knowledge is universal or nothing at all; second, that what these doctors call “empirical knowledge” is so lim­ited, unwieldly, chaotic, imprecise, and vague as not to merit the name of techne. Galen acknowledges that the rationalists have a point but he is con­fident they can be won over to his better account. He also thinks they down­play the limits of their own methods. Their theories are not all or even most of what practicing physicians need to know, and they lack the certainty and clarity that only experience adds.

Galen does not question the philosophical possibility of rational insight into nature's principles. But unlike the Stoics, he denies that such principles enjoy self-evidence. Nothing important to medical science is self-evident. Experience—“sensing of the body” (aisthesis tou somatos)—is the best cri­terion. When theory and experience clash we are admonished to seek the problem on the side of theory. “Experience is the ultimate judge,” Frede writes of Galen; “the rational method needs the check of experience. There are certain truths which are only found by experience.” The audacity of this thesis will become clear when we examine Aristotle on experience and scien­tific knowledge (§14).⁵¹

The limitation of empirical knowledge is that it affords no explanation why things had to be as experience finds them, lacking the necessity and univer­sality philosophers expect from episteme-science.

Empiricists did not deny that a doctor had to think and could not operate without logos. Ordinary thinking they called epilogismos, which they distin­guished from a special, technical, objectionably rationalistic analogismos, terms they borrow from Epicurean philosophy (§19). Rationalists say we need that special, technical analogismos reasoning—what they call a methodos logike—to perfect the medical art and make it properly scien­tific. As Galen explains it, this “rational method” depends on the supposed ability of reason to determine the kinds of things that exist and their essential qualities, using a special method of division or dichotomy. We owe our ac­count of this method to Plato, who describes it as “the method of medicine,” and recommended it as a good way to “determine the nature of something” without being “empirical and artless” about it:

Consider, then, what both Hippocrates and true argument say about na­ture. Isn't this the way to think systematically about the nature of anything? First, we must consider whether the object regarding which we intend to become experts and capable of transmitting our expertise is simple or com­plex. Then, if it is simple, we must investigate its power: what things does it have what natural power of acting upon? By what things does it have what natural disposition to be acted upon? If, on the other hand, it takes many forms, we must enumerate them all and, as we did in the simple case, inves­tigate how each is naturally able to act upon what and how it has a natural disposition to be acted upon by what....

This is the oldest idea of research method in European thought. In later incarnations it will be called the method of resolution and composition, or analysis and synthesis, or the regressus. According to Galen, Plato draws his account from the Hippocratic treatise On the Nature of Man, a work Galen regards as the philosophical foundation of Hippocrates’s whole teaching:

Hippocrates, having set himself the task to discover the nature of our bodies in this book, used the following method for his discovery: first he has inquired whether it is simple or complex, and then, having found that it is complex, examined the substance of the simple components contained in it, i.e., what sort of substance it is, that is, what power it possesses to be affected by something and to act.... In his research into the constituting elements of our body, he has kept in mind the elements of the whole, which are truly elements.⁵⁴

First we resolve a problem into simple parts. That is resolution or anal­ysis. Then we endeavor to show how, by the combination of these elem­ents, we can produce the phenomena, which is the moment of synthesis or composition, the Faustian, alchemical moment when we penetrate nature’s secrets and discover the key to an efficacy we can manipulate at will. From Plato and Galen, the method passed into medieval commentaries on Aristotle’s Posterior Analytics, and influenced Renaissance medical re­search at the school of Padua, where Galileo encountered and reformed it after the version he learned from newly available works of Alexandrian mathematics (§36). Descartes publicized Galileo’s renovated model in his Geometry, where he quotes the Alexandrian mathematician Pappus:

In the analysis, we assume the sought after as having been accomplished or done, inquiring out of what this results, and again, of the latter, we inquire for its predecessors, and so thus retracing, we arrive at something already known or something which is on the order of principles..

thesis, on the contrary, supposing the thing always perceived by the analysis as being already obtained, then disposing its consequences and its causes in their natural order, and then connecting them with one another, one at last arrives at the construction of the thing sought.⁵⁵

The text is more convoluted than Plato or Galen, but the idea is the same. The moment of analysis begins with the given phenomenon, the problem to be first resolved and ultimately solved. First, determine its cause; what did it come from? Then determine the cause of the cause. Repeat until arriving at something either already known or self-evident. The following, synthetic phase takes up the causes explicated by analysis to show that by connecting them in the right order, “one at last arrives at the construction of the thing sought.” Notice that this is what Euclid would classify as a problematic method (§1). It is set in motion by a problem, and terminates in a construc­tion that solves it.

Imposing this discipline on experience takes training. What character­ized the medical rationalists is trust in these special abilities and the training that inculcates them. Galen refused to extend that trust, influenced perhaps by the philosophical skepticism that matured in the context of Alexandrian medical empiricism. He is enough of an empiricist to react skeptically to un­tenable speculation about invisible causes. He is not anti-theory, but refuses to be drawn into the then already textbook questions of philosophy, like the essence of God, immortality, the eternity of the world, and the reality of void. Perhaps this is respect for the role of experience in science, for ex­perience seems unlikely ever to settle such questions. His exasperation with badly formed questions foreshadows Bacon and maybe even Rudolf Carnap. “In philosophy, it is not surprising that most disagreements have not been resolved,”

as the matters it deals with cannot be clearly judged by an empirical test, and therefore some say that the cosmos did not have a beginning, others that it had, and again some say that there is nothing outside surrounding it, and others that there is something................ Such disagreement cannot be settled

by clear sense-perception. But the case is not the same when a disagreement arises among doctors about the benefit or harm of remedies applied to bodies; physicians, at least, can judge by empirical test which of them is helpful and which is harmful.⁵⁶

Galen evidently felt the rationalist’s conviction that knowledge about causes—hidden, unobservable agents—is indispensable to the natural philosophy of medicine, while in technical medicine he concurs with the empiricists. Medicine has to respect what the body chooses to reveal, which can only be observed. The best physician combines logos and experience, but how does one do that? They seem incommensurable—how should we mix them? We seem to have to choose one sect or the other. Galen breaks the logjam with a new approach to empirical method, one that gives the rationalists the hidden causes they want, but without the certainty they have no right to expect. The idea of this method goes back to a text of Diocles of Carystus, a contemporary of Aristotle and second after Hippocrates in Greek medicine, though practically nothing of his writing survives. Prominent among the relics is a so-called Great Fragment on Method, which Galen preserved:

Those who think that one should state a cause in every case do not appear to understand first that it is not always necessary to do so from a practical point of view, and second that many things which exist are somehow by their nature akin to principles, so that they cannot be given a causal ac­count. Furthermore, they sometimes err in assuming what is unknown, disputed, and implausible, thinking that they have adequately given the cause. You should disregard people who aetiologize in this manner, and who think that one should state a cause for everything. You should rather rely on things which have been excogitated over a long period on the basis of experience (emperia), and you should seek a cause for contingent things when that is likely to make what you say about them more understandable and more believable.⁵⁷

Among other points, he criticizes the assumption that one should be able to offer a causal explanation of any medical phenomenon. It is not necessary, or not always necessary, for healing, and is superfluous when explanations reach the level of principles, for which there are no causes. He adds that an undisciplined chasing after causes can inadvertently lead the physician into murky water in a vain search for ever-deeper causes. Such physicians and their etiologies should be disregarded. Wise physicians rely on things they (and others) have carefully thought through on due experience. They seek tangible causes for tangible things that enhance medical understanding and a physician’s therapeutic options.

In context, Diocles was considering qualities and their dependence on a corporeal vehicle. Not every “hot” is the same—something depends on the body in question. His argument is that knowing the value of these qualities in their different materials takes experience. It is a mistake to abolish or refuse to consider causal explanations, but at the same time the explanations re­quire a disciplined practitioner. That is the idea Galen wants to extract and enlarge. The inquiry into causes must be controlled by what he calls quali­fied experience (disrismene peira). Galen produces a list of physicians from Hippocrates and Diocles to Erasistratus: “All of these acknowledge that what they know concerning medical practice they know by means of reasoning in conjunction with experience”—that is, qualified experience.⁵⁸

Qualified experience is a method by which experience checks what reason has guessed or expects. Experience is the criterion, source, and ultimate judge of knowledge, but only experience correctly used, with due qualifica­tion. In the quest for knowledge of the medical powers in foods and drugs, the physician’s experience has to be wide and systematic and not unqualified or without distinction (adioristos). We are advised to refuse simplistic etiolo­gies, not fix on single factors, and use distinctions to clarify what we expect to be causally relevant. Galen appreciates that Diocles’s advice is not limited to pharmacology; it would reduce experimental error everywhere in medicine, which even prompts a rare criticism of Hippocrates: “Some of the things written by him can be found to be lacking in qualification.” If Hippocrates made this mistake, lesser doctors have no hope. “Many others have in the same manner and for many parts and affections [of the body] described drugs without further qualification, not knowing what great power qual­ification (diorismos) has for the establishment of the art.” He says that the medicinal power of substances can be “clearly indicated by one experiential trial, and not any random trial, but one that has been carried out with the qualifications mentioned.”⁵⁹

Appropriate qualifications for judging pharmacological preparations are time and manner of preparation; condition of patient’s bowel and sto­mach; season, age, sex, lifestyle; whether the drug is to be taken in mixture with other substances or simple and pure; whether it is to be applied to dif­ferent parts of the body; and how it is to be administered for what kind of disease. Not all these qualifications can be observed, for example, a bad mix of humors or the state of the bowel, which has to be inferred from signs. The point of the qualifications is to distinguish essential (kath auto) from acci­dental (kath sumbebekos) factors. Galen opposes qualified experience both to reason alone (Bacon’s spiders, spinning webs from their own substance) and to experience without reason (Bacon’s ants, stocking away what they never digest). “For in general, it is not possible to test anything properly by experience without first discovering accurately by means of reason the con­dition of the body to which the food or drug that is being tested is applied”— discovered, he says, by means of reason, an empirical reason, and a use of experience that complements and does not resist rationality.⁶⁰

He is contemptuous of physicians (if there really were any) who place greater faith in analogismos-reasoning than experience. Galen imagines an empiricist addressing a rationalist: “Things for which you have no account of how they come to be you judge not to be, as reason demands. But to me, this very fact seems to be the most important objection to reason.” He alludes to the paradoxes Greeks discovered almost as soon as they discovered reason, like the sorites (one grain is not a heap, adding one grain does not make a heap, therefore heaps do not exist). Galen continues, “For who in his mind can still trust reason when it comes to matters which are not evident, if it is [so] devious as to postulate the contrary of what is obvious?” He almost sounds like Kant. Reason without experience is empty, experience without reason is blind (§55).⁶¹

Both discovery and evaluating what is found require the cooperation of reason and experience. Experience confirms what speculation invents, and is also an independent source of knowledge that reason would never find without hints a posteriori. Galen’s empiricist “not only uses definitions and determinations which rely solely on what is evident, but also makes use of causal accounts and proofs based on what has been ascertained antecedently by means of perception in an evident manner.” The result is an empirical medicine that can speak responsibly of causes and give rational explanations profound enough to guide physicians in healing.⁶²

Galen requires a spirit of inquiry (zetetikos) in a physician, and is confident that “nothing stands in the way of our becoming better than those before us.” Better even than Hippocrates. “Nothing prevents us from becoming not sim­ilar to Hippocrates but even better than he if first we learn the things that he wrote well and then ourselves search out what he omitted.” A good doctor is ever alert, ever posing questions to nature. “With constant practice, pursuing research, not just in an hour or so, but unceasingly throughout his whole life, he comes to penetrate whatever topic he chooses, reaching his goal by persis­tent inquiry into everything that might be relevant.”⁶³

He returns to this point more than once, evidently convinced that a pas­sion for inquiry would enhance not just medicine but natural philosophy. “Anyone who wants to know anything better than the ordinary run of hu­manity... must develop an almost erotic passion for the truth, so that day and night, like someone possessed, he will not let up in his desire and effort to learn what was propounded by the most illustrious of the ancients. And when he has learnt these things, he must spend a great deal of time testing and justifying them, seeing what accords with the observable facts and what does not” The expectation of inquiry and the progressive enhancement of natural knowledge is a consistent theme of ancient medical thought. One searches classical philosophy in vain for a comparable esteem for inquiry. In fact, Aristotle denies it. The happiest life is contemplating an achieved truth rather than inquiring.⁶⁴