rated a new epoch in chemistry by his remarkably sane and sound criticisms of the chemical thought and theories of the time. Boyle was a broadly and thoroughly trained scholar of the time, and prominent in many lines of activity. He was one of the founders of the Royal Society of England and at one time its president. He was also a man of wealth, but his main interest was in experimenting in chemistry and physics, and many notable observations stand to his credit. Every student of chemistry or physics knows of Boyle's law of gases.
It is not, however, by his experimental work—valuable as it was—that he exerted the greatest influence, but rather by his extended and frequent careful and scientific criticisms of the prevalent chemical theories, both the Aristotelian and Paracelsan theories, of the nature of substances and matter. Particularly by his work published in 1661 entitled "The Sceptical Chymist," in which, rather verbosely, but with great thoroughness and yet with great tolerance and patience, he submits the theories of the time to really constructive criticism. By a wealth of facts and experimental illustrations he demonstrates the purely metaphysical character of both the prevalent theories, and gradually develops the only consistent concept of an element which was possible for his time—namely, any substance which no experimental evidence could show to be reducible to simpler substances. He makes indeed, no attempt to say that any particular known substance is indeed an element in the sense of his characterization, though one might infer from his discussion that gold and silver were as well deserving of the title as any substances known to him, as he has never been able to obtain anything else from them or to know of any reliable experiments with such results. Unlike Paracelsus, or Glauber, or Van Helmont, or their imitators, Boyle was no dogmatist, being slow to assert and yet open-minded to any facts and very respectful to the opinions of others, though not in the least dominated by them.
The "Sceptical Chymist" of Boyle, as well as others of his writings, had a very wide circulation throughout the continent as well as in Great Britain, and his sane and persuasive reasoning, free from mysticism, and based on legitimate inferences from observed facts, made a great impression upon scientific men. While he offered no theory to replace the discredited Aristotelian and Paracelsan theories of the constitution of matter, he transferred the emphasis of chemical thought from a priori speculation to rational deductions from observed phenomena, and, though these might often be imperfect or mistaken, yet chemical reasoning was launched upon a course which could only lead to clearer understanding and to more soundly established theories.
The century following Boyle may be well characterized as the phlogistic period, because the representative chemists of that period were largely occupied in systematizing chemical actions with reference to that theory.
