§52. Physician Philosopher

The single use of a word with the root “empiri-,” as in empiricism, empirical, empiricist, and so on, in Locke’s Essay Concerning Human Understanding (1690) occurs in a context that suggests this is not a term with which he self­identifies.

We are not wrong to call Locke an empiricist, however, because the qualifi­cation comes to him as a physician of a markedly medical-empiricist persua­sion. Philosophers reading Locke often ignore his medical experience, yet his credentials were strong and he was acknowledged as a physician. Locke was at Oxford from 1652 until 1675, as a student, tutor, and lecturer. His interest in medicine emerged in the late 1650s. He met Boyle in 1660, and began taking notes on Boyle’s works, as well as reading Descartes and Gassendi. He also involved himself in the iatrochemical movement, inspired by Paracelsus but given weight by the more accomplished J. B. Van Helmont.

These chemical physicians called for a new instauration in physic. They deny the value of anatomy and elevate observation and experiment over the scholarly study of authorities, decrying hypotheses, and disdaining the mainstays of Galenic medicine, including phlebotomy and purging. However, to say only this overlooks Paracelsus’s new theory of elements and Helmont’s theory of the archeae.

It was this iatrochemical group that Locke allied with, beginning to ac­cumulate chemical notes and experiments in the latter 1650s. In Morbus, a manuscript from around 1666 in which he proposes an improbable recon­ciliation between Galen and Paracelsus, his view of disease is typical of the iatrochemists, above all Helmont. A note of skepticism appears in his next medical writing, Anatomia (1668), where Locke treats Helmont's archeae with disdain. This work was composed shortly after Locke made the ac­quaintance of Dr. Thomas Sydenham. Scholars routinely associate Locke with Boyle and Newton, whom he somewhat knew, but less usually with Sydenham, “the English Hippocrates,” with whom he was more intimate.¹⁸

Before 1667, when they met, medicine for Locke was a combination of re­quired Oxford lectures, private reading, and experimental work with friends, but no clinical experience until Sydenham introduced him to the bedside, convinced that this experience more than any scholarly learning made the physician. “You must go to the bedside, it is there alone that you can learn disease.” Locke accompanied Sydenham on professional visits and paid at­tention to his clinical method. They soon arrived at a plan to jointly write a treatise on smallpox. Though the book was unfinished, manuscripts from their collaboration survive.

Tis but ostentation & losse of time to lay downe hypothesis wch are many times false always uncertain & make a shew to enquire into the essences of things & pretend to shew the way & manner of their observacon[,] things that we cannot know being beyond the information of our senses or the reach of our understanding & therefor with very little advantage pretend to them.¹⁹

Sydenham's Methodus curandi febres (1666) was renamed Observationes medicae for an enlarged third edition (1676). A scholar who examined the three editions detects a change of tone in Sydenham's approach to medicine, presumably under Locke's influence. He was already diffident about etiology, or the causes of disease. In the first edition, before he even met Locke, he wrote, “Aetiology is a difficult, and perhaps inexplicable affair; and I choose to keep my hands clear of it.” Perhaps he became a more consistent empiricist with Locke to share experiences. The first edition had described smallpox as “a disease superinduced upon the blood during an attempt at a new status,” which he compared to molting. Having professed no liking for etiology, here he is with a theory of disease's unseen cause, what Greek medicine called a hypothesis. The theory of sanguineous molting disappears from the third edition, replaced by a sentiment more consistent with medical empiricism. “As to what may be the essence of smallpox, I am, for my own part, free to confess that I am wholly ignorant; this intellectual deficiency being the mis­fortune of human nature.”²⁰

It is not clear who is influencing whom. In 1666, before he met Sydenham, Locke collaborated with another physician in experiments and vivisections researching respiration, and wrote Respirationis usus, expounding a Helmontian chemical theory.

Writing to a physician friend, Locke says “the way of hypotheses” has “done more to hinder the true art of physick, which is the curing of disease, than all other things put together; by making it learned, specious, and talk­ative, but ineffective to its great end, the health of mankind.” To another he writes, “I perfectly agree with you concerning general theories, that they are for the most part but a sort of waking dream.... Nicely to observe the history of diseases in all their changes and circumstances, is a work of time, accurate­ness, attention, and judgment... the pattern Dr Sydenham has set.” Whether Locke fortified Sydenham’s aversion to hypotheses or vice versa, their collab­oration enhanced the commitment of each to medical empiricism.²²

Their work together ended in 1670, though Locke’s medical reading con­tinued, and he finally took his bachelor of medicine in 1675. He published his Essay in 1690, but the work was in manuscript by 1671, when he was engaged with medical thought and practice. From this time his Anatomia expresses the classical medical-empiricist disregard for anatomy, the stance that drew down reproaches from Celsus and Galen against the Alexandrian empiricists. The terms of the argument have not changed in fifteen hundred years.

But that anatomie is like to affording great improvement to the practise of physic, or assist a man in the findeing out and establishing a true method, I have reason to doubt.

The knowledge useful in medicine is a Hippocratic techne, “diligent ob­servation of those diseases, of their beginning, process, and ways of cure,” which requires no “scrupulous enquiry into the anatomye of the parts.” He carefully does not deny that the anatomist knows more than other doctors, “but not more to the purpose.” He “may perhaps be the better anatomist by multiplying dissections, but not a better physician.” The Hippocratic authors wrote at the beginning of their tradition, hopeful that the art would advance, though by Locke's time this medicine is two thousand years old and he is skeptical of a breakthrough. Anatomy gives not “much hopes of any greater improvement.” Even allowing for developments in op­tics, Locke thinks “the tools where with nature works and the changes she produces in these particles [are] too small and too subtle for the observa­tion of our senses.” Where Locke despairs of learning anything medically useful from studying the internal workings of the body, Leibniz is char­acteristically upbeat, judging it “probable” that “processes taking place in bodies” are not so complex “that we should despair of comprehending their inner composition.” “If an angel happened to reveal and explain them to us, we would wonder why we had not discovered them by ourselves.”²⁴

Where Bacon, Boyle, Descartes, and Leibniz expect great things from the union of experimental natural philosophy and medicine, Locke, Sydenham, and Newton see natural-philosophical hypotheses as an ir­responsible distraction. Locke excoriates the “searching out [of] hidden causes” and the fashioning of “systems and hypotheses,” which he blames for having “diverted [physicians'] enquiries from the true knowledge of things,” concluding elsewhere that “there is nothing left for a physician to do, but observe well.” Sydenham too declares “the investigation and illus­tration of primary and ultimate causes is a neglect of our capacities and a violation of nature.” He admires Boyle's attack on occult forms and his innovative pharmacology, but not the corpuscular hypothesis, which for his part Locke unenthusiastically allows as the least worst conjecture.

Locke's De arte medica (1669) emphasizes the futility of declaiming causes:

Proud man, not content with that knowledge which he was capable of and was useful to him, would needs penetrate into the hidden causes of things, lay down principles and establish maxims to himself about the operations of nature, and then vainly expect that nature, or in truth God himself, should proceed according to those laws his maxims had prescribed him; whereas his narrow, weak faculties could reach no further than the obser­vation and memory of some few effects produced by visible and external causes, but in a way utterly out of reach of his apprehension.²⁶

He limits medical knowledge to observation and memory—the classical definition of experience in Aristotle and Galen. Elsewhere in the treatise Locke refers to the question of “the knowledge of natural bodies,” such as is pursued in the Royal Society.

All speculations in this subject, however curious and refined, or seeming profound and solid, if they teach not their followers to do something either better or in a shorter or easier way than otherwise they could, or else lead them to the discovery of some new and useful invention, deserve not the name of knowledge.²⁷

The sublime useless quintessence of scientia has become for Locke a disqual­ification from knowledge.

Empirical, medical skepticism about invisible causes is a refrain in Locke’s Essay, whose earliest draft is dated two years after De arte medica. Locke does not share Bacon’s optimism for a new science of nature, and it is not his pur­pose in the Essay to lay down a philosophical foundation for such a science. On the contrary, he explains that “our business here is not to know all things, but those things which concern our conduct.” That does not include natural philosophy, which he says “is not capable of being made a science,” leaving him free to shift the center of gravity in philosophy to matters “from which we may draw advantages of ease and health.”²⁸

Locke distinguishes knowledge and judgment, loosely following Aristotle’s distinction between nous and phronesis. Knowledge is certain and nec­essary and answers to purely intellectual values, while judgment is for the conduct of life. Since the domain of “certain and demonstrative knowledge” falls notably short of “the greatest part of our concernments,” which are “the ordinary affairs of life,” we require good judgment to compensate for una­vailing knowledge. Judgment is the power to presume things to be so on the basis of probable but inconclusive evidence, or what Locke calls “assent to Probability.” His greatest departure from Aristotle is to associate natural phi­losophy with such judgment, and in that he is, consciously or not, following Gassendi, the Paduan physicians, and the nominalist tradition from Ockham and Buridan.

Nominalism was so pervasive at Oxford when Locke was an under­graduate that Oldenburg complained of it. Ockham's Summa logicae was reprinted there in 1675, the first new printing in a century. Scholars have noticed Locke's “unhesitating adherence to the nominalist tradition,” his nominalism being largely that of Ockham without the arguments. “General and Universal belong not to the real existence of Things; but are the Inventions and Creatures of the Understanding, made by it for its own use, and concern only Signs, whether Words or Ideas” There is no evidence that Locke actu­ally read Ockham, though Gassendi did and explicitly describes himself as a nominalist. For Locke the great idea of nominalism is that everything is indi­vidual, without need for a principle of individuation; nothing makes individ­uals to be individual. That is simply what being is.²⁹

Aristotle's dream of science in Posterior Analytics is unavailing. The con­triving and verifying of natural-philosophical hypotheses is more like med­ical prognosis than like geometry; a sedulous inquiry after causes produces no more than a sagacious conjecture. Expectations have to be moderated, as they would be for a medical prognosis. Demonstrably certain knowledge of universal propositions concerning substance “is very narrow and scanty” (Locke credits the cosmological proof of God). The future of natural philos­ophy is to be an art of conjectures made more or less probable by the “strength of judgment” proper to an “inquisitive and observing” philosopher.³⁰

The paradigm of this natural philosopher is a Hippocratic physician. We have a prestigious early example of medical judgment in a passage from the Hippocratic Epidemics.

The following were the circumstances attending the diseases, from which I framed my judgments, learning from the common nature of all, and the particular nature of the individual, from the disease, the patient, the reg­imen prescribed and the prescriber... from the constitution both of the whole and with respect to the parts... of the weather and of each region, from the customs, mode of life, practices and ages of each patient, from talk, manner, silence, thoughts, sleep or absence of sleep, the nature and time of dreams, pluckings, scratchings, tears; from the exacerbations, stools, urine, sputa, vomit, and antecedents and consequences of each member in the succession of diseases, and the abscessions to a fatal issue or a crisis, sweat, rigor, chill, cough, sneezes, hiccoughs, breathings, belching, flatulence, si­lent or noisy, haemorrages, and haemorroids. From these things we must consider what the consequents also will be.³¹

Good judgment distinguishes the professional physician from a quack, as a doctor of the early seventeenth century explains. “Good medicines are in themselves excellent instruments of health and life, but require a learned workman judiciously to guide them until their destined end.” Boyle also invokes medical judgment as a model for experimental natural philos­ophy, which had in his hands departed from the pretense of Aristotelian scientia. “Rational assent may be founded upon proofs, that reach not to rigid demonstrations, it being sufficient, that they are strong enough to de­serve a wise man’s acquiescence in them.” “The more things one knows by Experiment, the greater number he has of different Touch-stones (if I may so speak) or ways of discovering and judging, or (what is the result of both) of knowing, the nature of any thing proposed, that relate to it.”³²

A prudent physician is Locke’s model natural philosopher. “A man accus­tomed to regular and rational experiments shall be able to see farther into the Nature of Bodies, and guess righter at their as yet unknown properties, than one, that is a stranger to them; but yet... this is but a Judgment and Opinion, not Knowledge and Certainty.” It is therefore not science, not even properly called knowledge at all. “With me, to know and to be certain, is the same thing.... What reaches to knowledge, I think may be called certainty; and what comes short of certainty, I think cannot be called knowledge.” This was his consistent opinion and entirely orthodox.³³

What does it matter whether we call this new way of natural philosophy scientia and admit that we are changing usage, or abide by established use and refrain from calling experimental conclusions scientia? Why not cham­pion experimental natural philosophy as a more profound and promising knowledge than scientia ever managed to be? That is the point reached by Newton. “Although the arguing from experiments and observations by in­duction be no demonstration of general conclusions [i.e., not Aristotelian scientia], yet it is the best way of arguing which the nature of things admits of.” So, as the eighteenth century concluded, we might well call this inductive, empirical, experimental approach to natural philosophy science, as we still do, and forget that something unrecognizably different was ever called by the similar sounding name of scientia.³⁴