§42. A Philosopher of Qualities

Robert Boyle was a prolific experimenter, author of experimental nat­ural philosophy, and a founder of the Royal Society of London, the world's first scientific society (1666). He was also a pious Anglican, and among the wealthiest and best-connected Englishmen of his generation.

Gentlemen of Boyle's time also did not usually take up a reflective, reli­gious life. Boyle, who never married, describes the natural philosopher as a priest of nature. Every man is “born a priest of nature” “Reason is a nat­ural dignity, and knowledge a prerogative, that can confer priesthood without unction or imposition of hands.” His experimental philosopher is a Christian virtuoso, which to Boyle means, not a libertine, not a sensualist, not a mere “empiric,” or vulgar chemist, or one of those “who too often makes Experiments, without making Reflections on them, as having it more in his aim to Produce Effects, than to Discover Truths”¹⁵³

Boyle's virtuoso is always experimenting; indeed life itself becomes an experiment. “When I am employed about the duties and functions of a Christian... I am still but trying an experiment,” namely, whether the effort to live a Christian life can lead to “peace and conscience and contentment of mind in this life, and endless felicity in the next.” All his experimental work is an exercise in applied theology, seeking to make nature more thoroughly available for humanity, as ordained by God.

Boyle’s experimental virtuoso “is such a one, as by attentively looking about him, gathers Experience, not from his own Tryals alone, but from di­vers other matters of fact, which he heedfully observes, though he had no share in the effecting of them.” The explanation repeats a Hippocratic dis­tinction between autopsia, the physician’s observations, and istoria, corpo­rate medical experience. Boyle’s Hippocratic idea of experience embraces “all of those ways of Information, whereby we attain any Knowledge that we do not owe to abstracted Reason.” Experience is “the knowledge we have of any Matter of fact, which, without owing it to Ratiocination, either we acquire by the Immediate testimony of our Own Senses and other Faculties, or accrews to us by the Communicated Testimony of others.”¹⁵⁵

It was from jurisprudence that Europeans got their first experience in judging a balance of probabilities (§25). Medicine made empirical detail matter, and invented a method of evidence for hidden causes, though it was less inventive in dealing with complex and even contradictory evidence. It would not have been obvious that judicial procedures offered a better alter­native. Lawyers did not use them that way. Jurists are not trying to discover something, they are making a case; they require not new facts, but rather a proper dossier. They innovate the idea of assembling evidence and balancing probabilities, but the orientation is not empirical, as a method of disinter­ested discovery, but rather a method of administering justice. Who would think of using its proceedings to discover something really unknown?¹⁵⁶

Apparently no one before Francis Bacon, the experimenting lawyer. Following him, Boyle, Hooke, and their colleagues at the Royal Society con­ceive of experimental trials on the analogy of legal proceedings.

made up of particulars, that are each of them but probable; of which... the practice of our courts of justice here in England, affords us a manifest in­stance in the case of murder, and some other criminal cases. For, though the testimony of a single witness shall not suffice to prove the accused party guilty of a murder; yet the testimony of two witnesses, though but of equal credit, that is, a second testimony added to the first, though of itself never a whit more credible than the former, shall ordinarily suffice to prove a man guilty; because it is thought reasonable to suppose, that, though each testimony single be but probable, yet a concurrence of such probabilities, (which ought in reason to be attributes to the truth of what they jointly trend to prove) may well amount to a moral certainty.¹⁵⁷

We should remember that this novel coordination of experiments and ju­dicial proceedings takes place in England, home of the common law, which since its emergence in the twelfth century has considered itself the more “em­pirical” approach to law, open to experience. Roman law is “analytical,” while common law is “historical,” constraining individual reason by the experience embodied in actual judicial decisions collected over centuries. In the eyes of its practitioners, the superiority of common law was this openness to ex­perience, its ongoing conditioning by experience, which was considered to enhance law's regularity.¹⁵⁸

The common law offered a model of demonstration in which experience is fundamental to the reasonable resolution of cases. Experience has to guide the use of reason in the construction and application of law. This “experi­ence” is not mere accumulated fact but an appropriate technical interpreta­tion of facts. Mere reasoning is wholly incapable of deciding the law, which is very little like mathematics, and has its own methods of demonstration, su­perior (for law's purpose) to those of mathematics.

Boyle will always be associated with the founding and early career of the Royal Society of London. He was present at the inaugural meeting in London, November 28, 1660, in the Gresham College rooms of Lawrence Rooke, professor of astronomy. The declared intent of the founders was “the promoting of experimentall philosophy.” Experiment is emphasized. Earlier scientific academies performed them, collected them, praised them, but saw experimentation as a clandestine search for nature’s secrets. The Royal Society, at least in its publicity, is about the experiments themselves and perfecting the art of experimental natural philosophy. A statute, “Of Experiments, and Reports Thereof,” states: “In order to the propounding and making of experiments for the Society, consideration shall be had of the im­portance of any Experiment, to the discovery of any truth or axiom in nature, or to the use and benefit of mankind.”¹⁵⁹

The experiments they patronized reimagined the laboratory, transforming an alchemical tabernacle into a nondenominational space where experiments are performed, analyzed, and publicized. Royal Society apologists stress that theirs is a fellowship of free discussion only, with no allowance for sedition or irreligion. Their aim is consensus, which they pursue without imposing authority. Unsurprisingly, the Royal Society was less ecumenical in practice. Journalists, entrepreneurs, clerks, surgeons, and apothecaries are rare in the membership. “Enthusiasts & Phanatiques” were deliberately excluded, as was the infuriatingly disputatious Thomas Hobbes (§48). Yet they included Catholics, even in the Society’s active core (Kenelm Digby), and practicing Nonconformists, like William Penn.

In his experimental work and the books that publicized it, Boyle wanted to reform natural philosophy after Bacon’s plan and put it on an experimental footing. Natural philosophers should “forbear to establish any theory, till they have consulted with... a considerable number of experiments.” The accumulation of experiments had to be systematic, but experiments were superior to theories, which could never be more than provisional. That was Boyle’s “diffidence,” his willingness to remain suspended at “perhaps.” The genuinely pious Boyle was mortified by the atheism associated with materi­alist theories like his. It did not help that his contemporary, Thomas Hobbes, another proclaimed mechanist, had the unsavory reputation of an atheist. Boyle also had to defend his laboratory work against others no less keen to overthrow Aristotelianism, especially the Paracelsians.¹⁶¹

Boyle’s name for his theory of nature is “the corpuscularian hypothesis,” an expression he uses interchangeably with “mechanical hypothesis,” the word “corpuscularian” connoting particulate matter (but not indivisibles or true atoms), and “mechanical” connoting the twin principles of matter and mo­tion. His use of the word “corpuscle” reveals a debt to medicine, and he uses it for the same reason that medical authors introduced it, namely, to have all the usefulness of atomism without the dogma of indivisibility, which nobody had ever understood. Physicians of the ancient Methodist sect conceived the body as a porous structure of corpuscles, with health being a proper rela­tion of corpuscles and pores. One of these doctors, Asklepiades of Bithynia, knew of Aristotle’s refutation of atomism and named his minimal particles ongkoi, bulks. The knotty problem of infinite divisibility could for medical purposes be ignored. Corpuscula was introduced as Latin for ongkoi, min­imal constituents of natural bodies.¹⁶²

Boyle calls the corpuscularian theory a hypothesis, alluding to its provi­sional quality, which vexed Hobbes, whose idea of science remained that of Aristotle.

Boyle learned Italian to read Galileo’s Il Saggiatore (The Assayer). From Galileo he took the view that mechanical change is inherently intelligible, leaving qualitative change as the mystery and challenge to natural philos­ophy. He conceives a program of reducing qualities to quantities of corpus­cular motion, and it became his life’s work. Bacon had already proposed the collection of histories of qualities, meaning inventories, observations, and methodical classification, the point of which was eventually to explain quali­ties in corpuscular terms, along the lines of Bacon’s explanation of heat. Boyle takes up the work with a lifelong program of experimental research into the unseen quantities that cause qualities.¹⁶⁴

Whether qualities are mechanically generated by matter in motion is a question of fact and existence, not logic. It can be demonstrated only by experiments, and even then not infallibly. That is why hard metaphysical questions like the infinite divisibility of matter interest Boyle as little as they had Galen. How we answer them does not change the explanation of quali­ties. Whether matter is infinitely divisible makes no difference to the various ways that matter is qualified or the mechanical operations by which qualities are generated. Those are Boyle’s quarry. Infinite divisibility is his favorite ex­ample of a futile controversy that natural philosophers best ignore (Darwin felt that way about the origin of life).

Aristotle supplemented the Empedoclean elements (earth, air, fire, water) with Alcmaeon’s theory of qualities as pairs of opposites. The commentary tradition identifies as primae (first) qualities the pairs hot/cold and wet/dry. Natural change is change in these first qualities (that is what made Bacon’s reduction of heat to motion devastating for this theory of nature). Changes in these “primary” qualities transform the very elements themselves. Water heated becomes air, fire cooled becomes earth. Change in first qualities explains change in elements, and change in elements explains the rest. Later Aristotelians distinguished occult and manifest qualities, the former being hidden, insensible, and inexplicable in natural terms, with the magnetism of the lodestone as the favorite example. They also found a place for “real” qual­ities, qualities supposedly existing apart from the substance they qualify, an idea with a theological appeal that would not have interested Aristotle.

Boyle wants to elucidate the causes of qualities, which we do not observe, by reference to experimentally induced changes that we can observe. He rejects the idea of forms floating free of the material they qualify (“real” qual­ities), and thinks it hasty to pronounce any quality truly occult, that is, in­explicable. His hypothesis is that qualities can be explained mechanically as effects of corpuscular motion in invisible bodies. These sub-visible bodies are themselves variously qualified, and those qualities are Boyle’s new primae qualities. The first qualities are qualities of the corpuscles whose mechanical motion explains the rest. These first, primary qualities are not Aristotle’s hot, cold, moist, and dry, being instead the ineluctable qualities of a body merely as such, namely, extension, figure, and motion or rest.¹⁶⁵

What Boyle calls a “mechanical” explanation explains how structure is the cause of some given quality; for example, showing that the qualities of salts arise from the stiff, sharp texture of their particles. The cause is un­seen, but can be discovered by experience duly qualified by experimental method, though to deduce a single quality with full necessity and certainty is not possible for the reason Ockham had already stated. “The law of mo­tion... did not necessarily spring from the nature of matter, but depended upon the will of the divine author of things.” God is under no compulsion to produce qualities mechanically, and even if they are produced that way, they can always be produced directly by the power of God, or by arbitrarily dif­ferent mechanisms that experimenters might never discover. Boyle sees “no cause why blew & yellow for instance should make a green & not a pink nor a purple colour, but the laws which God freely establisht.”¹⁶⁶

Galileo is Boyle’s paragon in experimental philosophy, abstaining from systems but establishing laws. His unexpected discoveries with the telescope and his law of falling bodies exemplify the way “wherein we ascent to the experience even when its information seems contrary to reason,” Boyle ap­parently believing it was naively reasonable to think heavy bodies fall faster. “Notwithstanding this plausible ratiocination” experiments show something different. Galileo extols the wisdom of the assayer of gold, who ignores ob­vious appearances and carries out exacting tests, and ignores the single test to seek the concurrence of many.¹⁶⁷

For Boyle, natural philosophy is not just making experiments, it is making them well. He is contemptuous of thought experiments, insisting that “intri­cate and laborious experiments” must actually be performed. Consistently producing an effect in the laboratory is the best evidence that we understand the cause and have insight into its “form,” that is, the causally necessary and sufficient conditions. He appreciates repetition and variation, and favored the enhanced control obtained by experiments with purpose-built apparatus like a microscope or air pump. He also favored experiments that were performed in closed, transparent vessels, since one may “better know what concurs to the effects produced, because adventitious bodies... are kept from intruding upon those whose operations we have a mind to consider”¹⁶⁸