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.

Plot or Argument

• Praeface Introductory

  Boyle explains that the dialogue was written years earlier for a friend, partly lost, and published unfinished because chemical notions were being taken for granted by physicians and naturalists. He separates his respect for chemical experiments and remedies from his doubts about chemical theories of causes.

• Physiological Considerations: the meeting in the arbour

  The narrator and Eleutherius join Carneades, Themistius and Philoponus. Themistius argues from burning green wood that fire reveals the four elements; Philoponus argues for salt, sulphur and mercury. Carneades states the ground rules: he will examine their experiments, not propose his own system.

• The First Part: concessions about corpuscles

  Carneades grants four propositions favourable to some kind of principles: matter was divided at first into particles of various sizes and shapes; these formed small clusters; such clusters can survive many combinations; and a few kinds of them might make up many different bodies. Gold and quicksilver, recovered unchanged from many compounds, serve as examples.

• The Second Part: does fire separate or make?

  Carneades doubts that every substance obtained by fire pre-existed in the body. He reports plants grown in water alone, Helmont's willow, and the way fire can rearrange the parts of a body into new textures, so that analysis by fire may produce rather than reveal its products.

• The Third Part: the number of products

  Turning to the experiments themselves, Carneades argues that not all bodies yield three or four substances. Gold and silver resist analysis into salt, sulphur and mercury, while some vegetable and animal bodies yield five or more distinct products.

• The Fourth Part: the purity of products

  The substances called salt, sulphur and mercury are themselves mixed, retaining traces of the body they came from. Carneades complains that writers such as Paracelsus and Raymund Lully use their terms so loosely that no experiment can refute them.

• The Fifth Part: qualities left unexplained

  Claims of further purification grant his case. Carneades then argues that the three principles cannot account for the specific qualities of bodies, such as colour, smell and medicinal virtue, which depend more plausibly on the size, shape, motion and texture of their parts.

• The Sixth Part: are there elements at all?

  Pressed by Eleutherius, Carneades defines elements as primitive, simple, unmixed bodies and questions whether any such ingredient is common to all mixed bodies. He draws on Helmont's claims that water underlies all bodies and that the solvent called the alkahest can reduce them to their parts.

• The Conclusion

  Carneades admits his most radical paradox is less probable than his main argument, and compares chemists to Solomon's fleet of Tarshish, which brought home apes and peacocks with its gold. Eleutherius summarizes the points he thinks Carneades has made probable.

Characters

• Carneades, sceptic

  Host of the meeting, skilled with furnaces, who examines the chemists' and Aristotelians' proofs; generally taken as Boyle's spokesman.

• Eleutherius, interlocutor

  An open-minded friend who presses Carneades to go further and summarizes the argument at the end.

• Themistius, Aristotelian

  A learned defender of the four Peripatetic elements, who argues from burning green wood.

• Philoponus, chemist

  Defender of the three chemical principles of salt, sulphur and mercury.

• The narrator, reporter

  An unnamed visitor who records the conversation in the garden.

• Jan Baptist van Helmont, authority

  Flemish chemist and physician whose willow experiment and alkahest are discussed at length.

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.

  • What does Carneades grant in the First Part before he begins to object?
  • Why does he refuse to propose a complete system of his own?
  • How is Boyle's doubt different from simply rejecting what others say?

• 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.

  • What does Themistius think burning green wood proves, and how does Carneades answer?
  • What does Helmont's willow suggest about where a plant's substance comes from?
  • Can you think of a modern test whose results depend on an assumption that is easy to overlook?

• 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.

  • Why does Carneades say he hardly knows how to dispute with writers who use terms so loosely?
  • What makes Boyle's definition of an element precise enough to test?

• 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.

  • What is the point of Boyle's comparison with Solomon's ships bringing home apes and peacocks?
  • Is it possible for a remedy or technique to work well even when the theory behind it is wrong?

Context

In the mid-seventeenth century two theories of matter dominated learned discussion. University natural philosophy taught Aristotle's four elements and the qualities hot, cold, wet and dry, which also underlay Galenic medicine. The followers of Paracelsus taught that bodies are made of salt, sulphur and mercury, and used chemical preparations as medicines. At the same time a revived atomism, associated with Pierre Gassendi, and the mechanical philosophy of Descartes explained bodies by the size, shape and motion of particles. Boyle, a member of the Oxford circle that became the Royal Society, combined this corpuscular approach with extensive laboratory work.

Composition

Boyle says in the Preface that he had written the dialogue years earlier to satisfy a friend, that some papers were lost, and that he published it unfinished in 1661. It was printed in London by J. Cadwell for J. Crooke. The opening Physiological Considerations come from an earlier version of the first dialogue. A second edition (Oxford, 1680) added Experiments and Notes about the Producibleness of Chymicall Principles. A Latin translation spread the book on the Continent.

Reception

Nineteenth- and twentieth-century chemists often called the book a founding text of modern chemistry and Boyle's definition of an element a step toward Lavoisier. More recent historians, notably Lawrence Principe and William Newman, have stressed that Boyle remained deeply engaged with alchemy and that his target was chiefly the textbook chemists of his day, so that the book is better read as a critique of particular arguments than as a new theory of the elements. Both readings agree on its importance for the experimental and corpuscular style of the early Royal Society.

Comparisons

• lavoisier-elements-of-chemistry

  Boyle doubts that fire analysis reveals true elements; Lavoisier, over a century later, defines an element operationally as a substance not yet decomposed and builds a new chemical nomenclature, the clarity of terms that Boyle had demanded.

• novum-organum

  Bacon's call to clear away idols of the mind and to build knowledge from many careful experiments shaped the Royal Society; Boyle's critique of fire analysis is a practical example of that programme.

• on-the-nature-of-the-universe

  Lucretius explains all things by atoms of different shapes moving in the void; Boyle's First Part revives a particle account of matter while placing it within a Christian view of creation.

• galileo-selected-writings

  Galileo's Dialogue also sets an Aristotelian against a reformer before an open-minded third speaker; both authors use the dialogue form to argue against the schools while keeping the courtesy of conversation.

• aristotle-posterior-analytics-and-physics

  Themistius defends the Aristotelian elements and qualities whose foundations are laid in the Physics; reading the two shows what Boyle was arguing against.

• faraday-chemical-history-of-a-candle

  Themistius reads the four elements in burning wood; Faraday, two centuries later, uses a burning candle to teach the chemistry of combustion, water and carbon dioxide to young listeners.

Quotes

For Students

A reading companion for classical Christian high school students. See the student guide.

Reading Guide

Watch for

• The scene in the garden arbour where the narrator and Eleutherius find Carneades with Themistius and Philoponus, and the ground rules Carneades sets for the debate.
• Themistius's argument from a piece of green wood burning in a chimney, and how Carneades later turns the same furnace evidence against both schools.
• The four propositions of the First Part, where Carneades grants a particle theory of matter before he objects.
• The pumpkins and mint Boyle grew in water and Helmont's five-year willow experiment in the Second Part.
• The definition of an element at the start of the Sixth Part and the comparison with Solomon's ships in the Conclusion.

Key terms and names

Tria prima

The three chemical principles of the Paracelsians, salt, sulphur and mercury, which they claimed fire could separate out of every mixed body.

Peripatetick elements

The four elements of Aristotle's followers, earth, water, air and fire, defended in the dialogue by Themistius.

Mixt body

Boyle's term for any compound substance, such as wood, blood or a metal, as opposed to the simple ingredients it might be made of.

Corpuscles

The minute particles of matter, of various sizes and shapes, which Carneades thinks combine into clusters and textures that give bodies their qualities.

Spagyrist

A chemist of the Paracelsian school, especially one who prepares medicines by separating and recombining substances with fire.

Alkahest

The universal solvent claimed by Paracelsus and Helmont, said to reduce any body to its first matter; Carneades admits its existence is unproved.

Analysis by fire

The method of distilling or burning a body to separate its parts, which both Aristotelians and chemists took as proof of their theories.

Seminar Questions

1. Comprehension What evidence does Themistius offer for the four elements, and what evidence does Philoponus offer for the three principles?
2. Comprehension Why does Carneades think gold is a difficult case for the chemists?
3. Comprehension What did Helmont do with his willow tree, and what did he conclude?
4. Interpretation Carneades argues that fire may make new substances rather than reveal old ones. How does this one doubt undermine both the Aristotelian and the chemical theories at once?
5. Interpretation Why does Boyle write a dialogue with several speakers rather than a treatise in his own voice, and what does Carneades's courtesy toward his opponents add to the argument?
6. Interpretation In the Conclusion Carneades admits that his most radical paradox, that there may be no elements at all, is less probable than his main argument. What does that admission tell us about the kind of sceptic he is?
7. Big Question Boyle was a devout Christian who also doubted the scientific authorities of his day. Is the habit of questioning received opinion in natural science compatible with firm faith, and why?
8. Big Question When should we trust a practice that works even though its explanation is uncertain?

Faith Connections

• 1 Kings 10:22 (Scripture)

  Boyle's closing image comes from this verse, where Solomon's navy of Tarshish brings gold, silver, ivory, apes and peacocks. He uses it to say that chemists bring home valuable experiments along with showy or absurd theories.

• 1 Thessalonians 5:21 (Scripture)

  Paul's charge to prove all things and hold fast what is good fits Carneades's method: test each claim about the elements, keep the experiments that hold, and set aside the theories that do not.

• Proverbs 25:2 (Scripture)

  It is the glory of God to conceal a thing, and the honour of kings to search it out. Boyle and many of his Royal Society colleagues understood patient inquiry into nature as an honourable service of this kind.

• Robert Boyle, The Christian Virtuoso (1690) (Great Conversation)

  Late in life Boyle argued that experimental philosophy, by showing the wisdom of God in creation and training the mind in careful judgment, helps rather than hinders a man in being a good Christian.

Logic and Rhetoric

Central argument: Both the four-element and the three-principle theories rest on the claim that fire separates bodies into ingredients already present in them. But fire may produce new substances (as plants grown in water show), different bodies yield different numbers of products, gold yields none of the three principles, and the products obtained are themselves mixed. Therefore the analysis by fire does not prove that there are four elements or three principles, and it remains doubtful whether any determinate number of elements is found in all bodies.

Rhetorical device: concession (concessio). In the First Part Carneades grants four propositions in favour of some kind of principles before he begins his objections, and in the Conclusion he concedes that his most radical paradox is less probable than his main case; the concessions make his central doubts harder to dismiss.

Debate: Resolved: That an experiment can never prove a theory without first assuming another one.

Memory Work

Chymists have been much more happy in finding Experiments than the Causes of them; or in assigning the Principles by which they may best be explain'd.

if men would more carefully distinguish those things that they know, from those that they ignore or do but think

Writing Prompts

Essay: Boyle says that chemists have been better at finding experiments than at finding their causes. Using the green-wood argument, the willow experiment and the case of gold, explain how The Sceptical Chymist separates evidence from interpretation, and evaluate how persuasive Carneades's doubts are.

Comparison with Elements of Chemistry: Compare Boyle's definition of an element in the Sixth Part with Lavoisier's treatment of elements in the Preface to Elements of Chemistry. Argue whether Lavoisier answers the questions Boyle raised or changes the question.

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.

  Physicians Doctors Pharmacology Poisons
• 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.

  Pharmacology Poisons
• 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.

  Humoral Medicine Physicians Doctors
• The Fifth Part

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

  Pharmacology Poisons

Creative Prompts

• Dialogue

  Write a short scene in Carneades's arbour in which Philoponus returns and answers the argument from gold, which yields no salt, sulphur or mercury.

• Classroom

  Grow cuttings or bean seedlings in water alone for several weeks and weigh them, then discuss what Helmont concluded from his willow and what we now know about air, light and photosynthesis.

• Essay

  Compare Boyle's definition of an element with the one Lavoisier gave in 1789, and explain what changed in the meaning of the word.

Further Reading

• New Experiments Physico-Mechanicall, Touching the Spring of the Air, Robert Boyle

  The air-pump experiments of 1660.

• The Aspiring Adept: Robert Boyle and His Alchemical Quest, Lawrence M. Principe

  Argues that Boyle remained a serious student of alchemy.

• Boyle: Between God and Science, Michael Hunter

• Robert Boyle and Seventeenth-Century Chemistry, Marie Boas Hall

• Leviathan and the Air-Pump, Steven Shapin and Simon Schaffer

  On Boyle's experimental programme and its critics.