The Sceptical Chymist

Summary

The Sceptical Chymist is a philosophical dialogue in which Robert Boyle tests the two reigning theories of what bodies are made of: the four elements of the Aristotelians (earth, water, air and fire) and the three principles, or tria prima, of the Paracelsian chemists (salt, sulphur and mercury). Both schools appealed to the same evidence, the analysis of mixed bodies by fire. Boyle asks whether the substances that come out of the furnace were really in the body beforehand, and whether they are truly simple. The book opens with Physiological Considerations, part of an earlier dialogue. On a hot summer day the narrator and the inquisitive Eleutherius find Carneades in an arbour of his garden with two friends, the Aristotelian Themistius and the chemist Philoponus. Themistius points to green wood burning in a chimney, where flame, smoke, hissing moisture and ashes seem to display the four elements. Philoponus defends the three principles. Carneades agrees to play the sceptic and examine their proofs, not to set up a rival system. In the six Parts of the main treatise Carneades talks chiefly with Eleutherius. He first concedes several propositions: matter was originally divided into little particles of various sizes and shapes; these formed clusters that can persist through many combinations, as gold and quicksilver can be disguised in compounds and recovered unchanged. He then argues that fire may create new substances rather than release old ones, citing pumpkins and mint he grew in water alone and Jan Baptist van Helmont's willow, which gained over 160 pounds in five years while its soil lost almost nothing. He notes that gold yields no salt, sulphur or mercury, that different bodies yield different numbers of products, that the products are themselves mixed and impure, and that chemists use their terms so loosely that their claims cannot be tested. Nor, he argues, can the three principles explain colour, smell, taste and the other qualities of things. In the Sixth Part he defines elements as primitive, simple and unmixed bodies from which all mixed bodies are made, and questions whether any such ingredient is found in all of them. In the Conclusion Carneades says chemists have been better at finding experiments than at explaining them, and Eleutherius sums up what he thinks has been made probable. The book was printed in London in 1661 by J. Cadwell for J. Crooke; an enlarged edition followed in 1680. The library text is the complete 1661 first edition with its original spelling.

Top Lessons

• A sceptic can be a builder

  Carneades doubts the received theories but concedes what he can, gives his reasons, and admits when his own boldest paradox is weak. Boyle's scepticism is a method for clearing ground so that better knowledge can be built, not a refusal to believe anything.

• Ask what an experiment really shows

  Both Aristotelians and chemists pointed to the furnace. Boyle asks whether fire separates ingredients that were already there or makes new ones, and so shows that the same observation can be read in different ways depending on the assumption behind it.

• Clear words are part of honest science

  Boyle repeatedly complains that chemists write obscurely and use salt, sulphur and mercury in shifting senses. A claim that can mean anything cannot be tested. His insistence on plain definitions, culminating in his definition of an element, is one of the book's lasting contributions.

• Appreciating practical skill while questioning theory

  Boyle says he loves chemical experiments and values many chemical remedies, yet doubts the chemists' explanations of them. He shows that one can respect a craft's results while asking for better reasons.

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Medical Lens

Although the book is about chemistry, both theories it examines were medical theories. The four elements and their qualities underlay Galenic humoral medicine, and the three principles of salt, sulphur and mercury were the foundation of Paracelsian chemical medicine, whose distilled and mineral remedies were spreading among physicians in Boyle's day. Boyle's Preface warns that chemical notions were being adopted by eminent physicians without proof, while he insists that he values many chemical remedies. The text contains repeated reports of distilling human and deer blood into spirits, oils and salts, and discusses the physicians' view of chyle as the matter of blood. Boyle went on to write on medicine himself, notably Of the Reconcileableness of Specifick Medicines to the Corpuscular Philosophy (1685) and Medicinal Experiments, so the book belongs to the early history of pharmaceutical chemistry and of the separation of drug practice from drug theory.

• A Praeface Introductory

  Boyle warns that physicians and naturalists are adopting chemical theories uncritically, while affirming his esteem for chemical remedies.

• The First and Second Parts

  Accounts of distilling human blood and deer's blood into differing oils, spirits and salts, used to question whether the products existed beforehand.

• The Second Part

  Discussion of the physicians' teaching that chyle becomes blood and blood the parts of the body, as an analogy for the transformation of matter.

• The Fifth Part

  Carneades argues that specific qualities of bodies, including medicinal virtues, are not explained by salt, sulphur and mercury.