Elements and Atoms: Chapter 2
Robert Boyle, a Sceptical Chymist

Robert Boyle was the seventh son of Richard Boyle, the greatest landlord in Ireland in the early 17th century, known as the "Great Earl of Cork." The younger Boyle was an important natural philosopher, a founder and influential fellow of Britain's Royal Society who made important contributions in both physics and chemistry. (View a portrait of Boyle at the National Portrait Gallery, London.) He is probably best known today for "Boyle's law," [Boyle 1662] which relates the pressure and volume of gases. (View some of his apparatus for investigating gases at Stanford University.) His earliest publication was on the physical properties of air; he also wrote detailed accounts of chemical experiments, including several on combustion [Boyle 1672].

The Sceptical Chymist, which is excerpted below, is a long dialogue concerning the nature and number of the elements. Boyle does not know how many elements there are or what those elements may be; however, he argues that those who believe the elements to be earth, air, fire, and water (following Aristotle and the ancients) or mercury, sulfur, and salt (following more recent alchemical doctrine) do so on an insufficient basis. The cast of characters includes Carneades (representing Boyle's opinions), Themistius (representing the four-element system of the ancients), Philoponus (representing the three-principle system of the alchemists), and Eleutherius (an interested observer).

from The Sceptical Chymist, London, 1661

The experiments wont to be employed to evince either the IV Peripatetick Elements[2], or the III Chymical Principles[3] of Mixt Bodies[4]

Part of the First Dialogue.[5]


[pp. 13-17]

Philoponus and Themistius soon returned this complement with civilities of the like nature, in which Eleutherius perceiving them engaged, to prevent the further loss of that time of which they were not like to have very much to spare, he minded them that their present businesse was not to exchange complements, but Arguments: and then addressing his speech to Carneades, I esteem it no small happinesse (saies he) that I am come here so luckily this Evening.[6] For I have been long disquieted with Doubts concerning this very subject which you are now ready to debate. And since a Question of this importance is to be now discussed by persons that maintain such variety of opinions concerning it, and are both so able to enquire after truth, and so ready to embrace it by whomsoever and on what occasion soever it is presented them; I cannot but promise my self that I shall before we part either lose my Doubts or the hopes of ever finding them resolved: Eleutherius paused not here; but to prevent their answer, added almost in the same breath[7]; and I am not a little pleased to find that you are resolved on this occasion to insist rather on Experiments than Syllogismes.[8] For I, and no doubt You, have long observed, that those Dialectical subtleties, that the Schoolmen too often employ about Physiological Mysteries, are wont much more to declare the wit of him that uses them, then increase the knowledge or remove the doubts of sober lovers of truth. And such captious subtleties do indeed often puzzle and sometimes silence men, but rarely satisfy them. Being like the tricks of Jugglers, whereby men doubt not but they are cheated, though oftentimes they cannot declare by what flights they are imposed on. And therefore I think you have done very wisely to make it your businesse to consider the Phaenomena relating to the present Question, which have been afforded by experiments, especially since it might seem injurious to our senses, by whose mediation we acquire so much of the knowledge we have of things corporal, to have recourse to far-fetched and abstracted Ratiocination, to know what are the sensible ingredients of those sensible things that we daily see and handle, and are supposed to have the liberty to untwist (if I may so speak) into the primitive bodies they consist of. He annexed that he wished therefore they would no longer delay his expected satisfaction, if they had not, as he feared they had, forgotten something preparatory to their debate; and that was to lay down what should be all along understood by the word Principle or Element. Carneades thank'd him for his admonition, but told him that they had not been unmindful of so requisite a thing. But that being Gentlemen and very far from the litigious humour of loving to wrangle about words or terms or notions as empty; they had before his coming in, readily agreed promiscuously to use when they pleased, Elements and Principles as terms equivalent: and to understand both by the one and the other, those primitive and simple Bodies of which the mixt ones are said to be composed, and into which they are ultimately resolved.[9] And upon the same account (he added) we agreed to discourse of the opinions to be debated, as we have found them maintained by the Generality of the assertors of the four Elements of the one party, and of those that receive the three Principles on the other, without tying our selves to enquire scrupulously what notion either Aristotle or Paracelsus[10], or this or that Interpreter, or follower of either of those great persons, framed of Elements or Principles; our design being to examine, not what these or those thought or taught, but what we find to be the obvious and most general opinion of those, who are willing to be accounted Favourers of the Peripatetick or Chymical Doctrine, concerning this subject.[11]


[pp. 347-352]

A Paradoxical Appendix to the Foregoing Treatise.

The Sixth Part.

Here Carneades Having Dispach't what he Thought Requisite to oppose against what the Chymists are wont to alledge for Proof of their three Principles, Paus'd awhile, and look'd about him, to discover whether it were Time for him and his Friend to Rejoyne the Rest of the Company. But Eleutherius perceiving nothing yet to forbid Them to Prosecute their Discourse a little further, said to his Friend, (who had likewise taken Notice of the same thing) I halfe expected, Carneades, that after you had so freely declar'd Your doubting, whether there be any Determinate Number of Elements, You would have proceeded to question whether there be any Elements at all.[12] And I confess it will be a Trouble to me if You defeat me of my Expectation; especially since you see the leasure we have allow'd us may probably suffice to examine that Paradox; because you have so largly Deduc'd already many Things pertinent to it, that you need but intimate how you would have them Apply'd and what you would inferr from them.

Carneades having in Vain represented that their leasure could be but very short, that he had already prated very long, that he was unprepared to maintain so great and so invidious a Paradox, was at length prevail'd with to tell his Friend; Since, Eleutherius, you will have me Discourse Ex Tempore of the Paradox[13] you mention, I am content, (though more perhaps to express my Obedience, then my Opinion) to tell you that (supposing the Truth of Helmonts[14] and Paracelsus's Alkahestical[15] Experiments, if I may so call them) though it may seem extravagant, yet it is not absurd to doubt, whether, for ought has been prov'd, there be a necessity to admit any Elements, or Hypostatical[16] Principles, at all.

And, as formerly, so now, to avoid the needless trouble of Disputing severally with the Aristotelians and the Chymists, I will address my self to oppose them I have last nam'd, Because their Doctrine about the Elements is more applauded by the Moderns, as pretending highly to be grounded upon Experience.[17] And, to deal not only fairly but favourably with them, I will allow them to take in Earth and Water to their other Principles. Which I consent to, the rather that my Discourse may the better reach the Tenents of the Peripateticks; who cannot plead for any so probably as for those two Elements; that of fire above the Air being Generally by Judicious Men exploded as an Imaginary thing; And the Air not concurring to compose Mixt Bodies as one of their Elements, but only lodging in their pores, or Rather replenishing, by reason of its Weight and Fluidity, all those Cavities of bodies here below, whether compounded or not, that are big enough to admit it, and are not fill'd up with any grosser substance.[18]

And, to prevent mistakes, I must advertize You, that I now mean by Elements, as those Chymists that speak plainest do by their Principles, certain Primitive and Simple, or perfectly unmingled bodies; which not being made of any other bodies, or of one another, are the Ingredients of which all those call'd perfectly mixt Bodies are immediately compounded, and into which they are ultimately resolved: now whether there be any one such body to be constantly met with in all, and each, of those that are said to be Elemented bodies, is the thing I now question.[19]

By this State of the controversie you will, I suppose, Guess, that I need not be so absurd as to deny that there are such bodies as Earth, and Water, and Quicksilver, and Sulphur: But I look upon Earth and Water, as component parts of the Universe, or rather of the Terrestrial Globe, not of all mixt bodies. And though I will not peremptorily deny that there may sometimes either a running Mercury, or a Combustible Substance be obtain'd from a Mineral, or even a Metal; yet I need not Concede either of them to be an Element in the sence above declar'd;[20] as I shall have occasion to shew you by and by.

To give you then a brief account of the grounds I intend to proceed upon, I must tell you, that in matters of Philosophy, this seems to me a sufficient reason to doubt of a known and important proposition, that the Truth of it is not yet by any competent proof made to appear. And congruously herunto, if I shew that the grounds upon which men are perswaded that there are Elements are unable to satisfie a considering man, I suppose my doubts will appear rational.[21]


[pp. 427-36]


These last Words of Carneades being soon after follow'd by a noise which seem'd to come from the place where the rest of the Company was, he took it for a warning, that it was time for him to conclude or break off his Discourse; and told his Friend; By this time I hope you see, Eleutherius, that if Helmonts Experiments be true, it is no absurdity to question whether that Doctrine be one[22], that doth not assert Any Elements in the sence before explain'd. But because that, as divers of my Arguments suppose the marvellous power of the Alkahest in the Analyzing of Bodies, so the Effects ascrib'd to that power are so unparallell'd and stupendious, that though I am not sure but that there may be such an Agent, yet little less than αυτοψια seems requisite to make a man sure there is. And consequently I leave it to you to judge, how farre those of my Arguments that are built upon Alkahestical Operations are weakened by that Liquors being Matchless; and shall therefore desire you not to think that I propose this Paradox that rejects all Elements, as an Opinion equally probable with the former part of my discourse. For by that, I hope, you are satisfied, that the Arguments wont to be brought by Chymists, to prove That all Bodies consist of either Three Principles, or Five, are far from being so strong as those that I have employ'd to prove, that there is not any certain and Determinate number of such Principles or Elements to be met with Universally in all mixt Bodies.[23] And I suppose I need not tell you, that these Anti-Chymical Paradoxes might have been manag'd more to their Advantage; but that having not confin'd my Curiosity to Chymical Experiments, I who am but a young Man, and younger Chymist, can yet be but slenderly furnished with them, in reference to so great and difficult a Task as you impos'd upon me; Besides that, to tell you the Truth, I durst not employ some even of the best Experiments I am acquainted with, because I must not yet disclose them; but however, I think I may presume that what I have hitherto Discoursed will induce you to think, that 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.[24] And indeed, when in the writings of Paracelsus I meet with such Phantastick and Un-intelligible Discourses as that Writer often puzzels and tyres his Reader with, father'd upon such excellent Experiments, as though he seldom clearly teaches, I often find he knew; me thinks the Chymists, in their searches after truth, are not unlike the Navigators of Solomons Tarshish Fleet, who brought home from their long and tedious Voyages, not only Gold, and Silver, and Ivory, but Apes and Peacocks too[25]; For so the Writings of several (for I say not, all) of your Hermetick Philosophers present us, together with divers Substantial and noble Experiments, Theories, which either like Peacocks feathers make a great shew, but are neither solid nor useful; or else like Apes, if they have some appearance of being rational, are blemish'd with some absurdity or other, that when they are Attentively consider'd, makes them appear Ridiculous.

Carneades having thus finish'd his Discourse against the received Doctrines of the Elements; Eleutherius judging he should not have time to say much to him before their separation, made some haste to tell him; I confess, Carneades, that you have said more in favour of your Paradoxes than I expected. For though divers of the Experiments you have mention'd are no secrets, and were not unknown to me, yet besides that you have added many of your own unto them, you have laid them together in such a way, and apply'd them to such purposes, and made such Deductions From them, as I have not Hitherto met with.[26]

But though I be therefore inclin'd to think, that Philoponus, had he heard you, would scarce have been able in all points to defend the Chymical Hypothesis against the arguments wherewith you have oppos'd it; yet me thinks that however your Objections seem to evince[27] a great part of what they pretend to, yet they evince it not all; and the numerous tryals of those you call the vulgar Chymists, may be allow'd to prove something too.

Wherefore, if it be granted you that you have made it probable,[28]

First, that the differing substances into which mixt Bodies are wont to be resolved by the Fire are not of a pure and an Elemenentary nature, especially for this Reason, that they yet retain so much of the nature of the Concrete[29] that afforded them, as to appear to be yet somewhat compounded, and oftentimes to differ in one Concrete from Principles of the same denomination in another:

Next, that as to the number of these differing substances, neither is it precisely three, because in most Vegetable and Animal bodies Earth and Phlegme are also to be found among their Ingredients; nor is there any one determinate number into which the Fire (as it is wont to be employ'd) does precisely and universally resolve all compound Bodies whatsoever, as well Minerals as others that are reputed perfectly mixt.

Lastly, that there are divers Qualities which cannot well be refer'd to any of these Substances, as if they primarily resided in it and belong'd to it; and some other qualities, which though they seem to have their chief and most ordinary residence in some one of these Principles or Elements of mixt Bodies, are not yet so deducible from it, but that also some more general Principles must be taken in to explicate them.[30]

If, I say, the Chymists (continues Eleutherius) be so Liberall as to make you these three Concessions, I hope you will, on your part, be so civil and Equitable as to grant them these three other propositions, namely;

First, that divers Mineral Bodies, and therefore probably all the rest, may be resolv'd into a Saline, a Sulphureous, and a Mercurial part; And that almost all Vegetable and Animal Concretes may, if not by the Fire alone, yet, by a skilfull Artist Employing the Fire as his chief Instrument, be divided into five differing Substances, Salt, Spirit, Oyle, Phlegme and Earth; of which the three former by reason of their being so much more Operative than the Two Later, deserve to be Lookt upon as the Three active Principles, and by way of Eminence to be call'd the three principles of mixt bodies.[31]

Next, that these Principles, Though they be not perfectly Devoid of all Mixture, yet may without inconvenience be stil'd the Elements of Compounded bodies, and bear the Names of those Substances which they most Resemble, and which are manifestly predominant in them; and that especially for this reason, that none of these Elements is Divisible by the Fire into Four or Five differing substances, like the Concrete whence it was separated.[32]

Lastly, That Divers of the Qualities of a mixt Body, and especially the Medical Virtues, do for the most part lodge in some One or Other of its principles, and may Therefore usefully be sought for in That Principle sever'd from the others.[33]

And in this also (pursues Eleutherius) methinks both you and the Chymists may easily agree, that the surest way is to Learn by particular Experiments, what differing parts particular Bodies do consist of, and by what wayes (either Actual or potential fire) they may best and most Conveniently be Separated, as without relying too much upon the Fire alone, for the resolving of Bodies,[34] so without fruitlessly contending to force them into more Elements than Nature made Them up of, or strip the sever'd Principles so naked, as by making Them Exquisitely Elementary to make them almost useless,[35]

These things (subjoynes Eleu.) I propose, without despairing to see them granted by you; not only because I know that you so much preferr the Reputation of Candor before that of subtility, that your having once suppos'd a truth would not hinder you from imbracing it when clearly made out to you; but because, upon the present occasion, it will be no disparagement to you to recede from some of your Paradoxes, since the nature and occasion of your past Discourse did not oblige you to declare your own opinions, but only to personate an Antagonist of the Chymists. So that (concludes he, with a smile) you may now by granting what I propose, add the Reputation of Loving the truth sincerely to that of having been able to oppose it subtilly.

Carneades's haste forbidding him to answer this crafty piece of flattery; Till I shal (sayes he) have an opportunity to acquaint you with my own Opinions about the controversies I have been discoursing of, you will not, I hope, expect I should declare my own sence of the Arguments I have employ'd. Wherefore I shall only tell you thus much at present; that though not only an acute Naturalist, but even I my self could take plausible Exceptions at some of them; yet divers of them too are such as will not perhaps be readily answer'd, and will Reduce my Adversaries, at least, to alter and Reform their Hypothesis. I perceive I need not minde you that the Objections I made against the Quaternary of Elements and Ternary of Principles needed not to be oppos'd so much against the Doctrines Themselves (either of which, especially the latter, may be much more probably maintain'd than hitherto it seems to have been, by those Writers for it I have met with) as against the unaccurateness and the unconcludingness of the Analytical Experiments vulgarly Relyed On to Demonstrate them.[36]

And therefore, if either of the two examin'd Opinions, or any other Theory of Elements, shall upon rational and Experimental grounds be clearly made out to me; 'Tis Obliging, but not irrational, in you to Expect, that I shall not be so farr in Love with my Disquieting Doubts, as not to be content to change them for undoubted truths. And (concludes Carneades smiling) it were no great disparagement for a Sceptick to confesse to you, that as unsatisfy'd as the past discourse may have made you think me with Doctrines of the Peripateticks, and the Chymists, about the Elements and Principles, I can yet so little discover what to acquiesce in, that perchance the Enquiries of others have scarce been more unsatisfactory to me, than my own have been to my self.[37]



[1]Here physiological means "relating to the material universe or to natural science, phyiscal" rather than "relating to the functions and properties of living bodies" [Oxford 1971].

[2]Peripatetic refers to Aristotle's school of philosophy. Aristotle believed in four elements: earth, air, fire, and water. (See previous chapter.)

[3]A modern writer would use alchemical in many places where Boyle uses chymical. According to the alchemist Paracelsus (see note 10 below) and his followers, there were three elements, or as they called them, principles: sulfur, mercury, and salt. Sulfur was associated with combustible substances, mercury with metals, and salt with fixity.

[4]The term mixed bodies encompasses both relatively pure chemical compounds and complicated composites of such compounds. Compounds are materials homogeneous on an atomic scale formed by the intimate bonding of elements in definite proportions. Minerals are examples of relatively pure compounds which were chemically analyzed in Boyle's time. Homogeneous mixtures such as the gases which comprise air or a solution of sugar in water also involve mixing of elements on a microscopic scale, but no chemical bonding. Biological substances such as meat (animal muscle) or plant tissue are examples of still more complicated composites, which were also subjected to chemical analysis.

[5]The dialogue is not the usual genre for scientific communication. The usual form employs detailed description of experimental procedures and observations. Boyle used this style as well, and in some ways helped set standards for it [Conant 1957]. Boyle, however, had ample precedent in his day for the dialogue form. Plato's dialogues set the precedent for the genre in philosophy, and science in the 17th century was essentially a branch of philosophy (natural philosophy). Galileo's dialogues are perhaps the best known in science [Galilei 1632, Galilei 1634]. The Sceptical Chymist was not the last dialogue on chemical subjects: for example, Humphry Davy wrote some [Davy 1840]. Modern dialogues concerning science self-consciously allude to earlier examples (for example, Bronowski 1956).

[6]To the reader who is accustomed to the direct narrative of modern scientific communication, The Sceptical Chymist presents several challenges besides the dialogue form. The prose style of the time was flowery and complex. Boyle makes a point of employing a friendly dialogue so as to allow the clashing of ideas without the harsh polemics which often crept into learned treatises. As a result, there are many exchanges of compliments and civilities. The sentence structure imitates classical Latin models in deploying multiple subordinate clauses. The modern reader must also contend with unfamiliar words as well as familiar words with unfamiliar spellings, as with any text from Restoration England (e.g., complement for compliment). An attentive reader will also notice unfamiliar and unsystematic patterns of capitalization. Readers of editions that date back to Boyle or of facsimile editions would also notice a character resembling "f" used for lower-case "s" except at the end of a word.

[7]Eleutherius wishes to develop an informed opinion concerning the elements. He plays the part of an active student, moving the discussion along and keeping the other participants on task.

[8]What evidence will be allowed in this discussion? Whatever the conclusion, it is to be supported by empirical evidence, not rationalistic argument (e.g., syllogisms). This is an important point, for Aristotle's arguments were mainly rationalistic. (See previous chapter.) And even though the Alchemical principles claim to be based on empirical evidence, Carneades will show deficiencies in the interpretation of experiments on which the alchemical system is based.

[9]Before debating the nature and number of the elements, it is important to define what is meant by element. The participants in the debate will agree to treat the terms element and principle as interchangeable. (The Peripatetics usually used "element," and this term is the one in current usage; the alchemists used "principle.") An element is a simple substance, a building block for more complex substances. Complex bodies are formed from elements, and can be resolved into those elements by analysis.

This definition is a bit more restrictive than that proposed by Lavoisier in the late 18th century (See next chapter.), for it implies not only that elements cannot be broken down into simpler substances, but also that they combine with each other to form complex substances. (See note 18 below.) Tenney Davis notes that the definition of element is not a subject of dispute in The Sceptical Chymist, and argues that it was already widely accepted in Boyle's time [Davis 1931]. Indeed, even Aristotle gave a definition remarkably like Boyle's [Aristotle Caelo]: "An element, we take it, is a body into which other bodies may be analysed, present in them potentially or in actuality (which of these, is still disputable), and not itself divisible into bodies different in form."

[10]Paracelsus (1493-1541; view portraits in Jack Lynch's site, University of Pennsylvania), also known as Theophrastus von Hohenheim, was a physician who rejected many of the tenets of classical medicine. Among his innovations was the application of chemical substances to treat medical conditions (such as mercury to treat syphillis). His alchemical writings, like many of the time, contain a mixture of mysticism and experiment.

[11]The debate will not be historical, about who said what about the elements and when. It will examine the version of the Peripatetic and alchemical systems of elements as commonly taught and understood in Boyle's time.

[12]By this point in the dialogue, Carneades has raised doubts about the Peripatetic and alchemical beliefs on the elements, criticizing the evidence on which those beliefs were grounded. He has been so successful in raising doubts that Eleutherius wonders whether there is good reason to believe elements exist at all.

[13]One of the meanings of paradox current in Boyle's time but rare since the 17th century was "a statement or tenet contrary to received opinion or belief" [Oxford 1971]. A paradox, then, need not be or seem self-contradictory. The paradox to which Carneades refers is the doubt whether there are such things as elements. He will proceed to defend this skepticism, or at least to show it is plausible ("not absurd").

[14]van Helmont (1580-1644; view portrait at National Library of Medicine) was a transitional figure between alchemy and chemistry, combining belief in the philosopher's stone with careful observation and experimentation. He believed water was the primary element. In support of this belief, he observed that a tree planted in a measured amount of soil to which nothing but water had been added increased in weight well over 100 pounds while the soil lost only a few ounces.

[15]Alkahest is a term invented by Paracelsus to denote a universal solvent. The context suggests that Carneades refers to experiments of chemical analysis, in which a complex body is broken down into its simpler substances.

[16]Here hypostatical means "of or pertaining to the essential principles or elements of bodies; elemental" [Oxford 1971].

[17]The Peripatetic set of four elements and its rationalistic basis was already falling out of favor. Carneades will focus his doubts on the existence of elements on the most plausible proposed elements, namely those of the alchemists plus water and earth (the more plausible of the Peripatetic set). He dispenses with fire and air in just a couple of sentences.

[18]Note why Carneades does not consider air to be an element. He does not argue that air is itself a compound or mixed body, capable of being broken down into simpler material. Rather, he says air does not enter into combination with other substances to give rise to compound bodies; air is not a building block of compounds. Had 19th-century scientists followed Boyle's definition of an element rather than Lavoisier's similar but not identical formulation, they would not have considered argon and its related noble gases to be elements. (See chapter 14.)

[19]The question to which Carneades addresses himself is whether there is any element found in all "Elemented bodies" (i.e., compound bodies, for elemented means "composed of elements," not "elementary"). The notion of being a component of all compounds is certainly no longer part of the idea of element. It appears to be a remnant from the Aristotelian conception in which complex bodies were formed of all four elements, actually or potentially present to various degrees; it is not explicit in the definition which forms the first part of this paragraph or in the definition given near the beginning of the treatise (see note 9).

[20]Of course substances such as water and sulfur exist. These substances even result from analysis of some minerals and metals. But they do not seem to be ingredients of all complex materials.

[21]Carneades intends only to show that his doubts are reasonable. His standard for establishing an idea in science appears to be similar to that required to convict in an American criminal trial: evidence which overcomes reasonable doubt.

[22]I.e., an absurdity. Carneades cleverly (if confusingly) says that if van Helmont is right, then elements do exist. But the evidence which would lead to this conclsion depends on the existence of the Alkahest, a dubious proposition in itself. The Alkahest is supposed to have such unusual powers that little short of seeing it for oneself (αυτοψια) would be convincing.

[23]Carneades' opinion on whether any elements exist can be termed agnostic; he seems to be saying here that there are no convincing arguments either for or against. This is in contrast to his stronger skepticism concerning the notion that there is a set number of elements (such as the four of the ancients or the three of the alchemists).

[24]The alchemists, Carneades says, performed some good experiments. Their interpretations of experiment, however, left much to be desired. The alchemists were like modern scientists in that they performed experiments and made observations; they were, by and large, unlike modern scientists in trying to make connections between the observable but mysterious chemical changes and the unobservable mysteries of a preconceived philosophical system. Experiments were not so much means by which the natural world could be understood as tangible connections to deeper mysteries.

[25]I Kings 10:22. Boyle no doubt alludes to the King James version; more recent translations substitute monkeys for peacocks. At any rate, it is interesting to see Boyle draw a distinction between the presumably valuable minerals and the showy or ridiculous animals which is absent in the original, for in Kings the entire list is meant to convey the wealth of Solomon.

[26]In effect, Eleutherius makes the point that reliable science does not consist simply of gathering facts, for the facts alone do not speak for themselves. Indeed Carneades has just made a similar point, approving of the experiments of the alchemists but finding fault with their interpretations. Here Eleutherius compliments Carneades for arranging the experiments in such a way as to be able to draw some meaningful conclusion from them.

[27]Here evince means "confute, convict of error" [Oxford 1971]. Thus Eleutherius suggests that Carneades has successfully argued that the experiments of the alchemists do not prove what they purport to prove, but has not shown them to be completely worthless.

[28]Eleutherius is about to distill several working hypotheses out of the preceding discussion. Note that he characterizes the propositions as "probable," not as established. The standard of evidence required to consider a proposition as established is, as noted above (note 21), quite high. It is not necessary, however, for scientists to suspend belief completely in the absence of such evidence. It is often useful to hold propositions such as the following as working hypotheses, probable but provisional. It is fair to say that these propositions were useful in pursuing chemical analysis experimentally, but that they are largely irrelevant to the much more detailed and developed analytical methods used today.

[29]Here concrete carries the connotation of composite much more strongly than the connotations of tangible or solid which are more common in modern usage. Thus a concrete is a compound body. Eleutherius suggests that what results when such bodies are broken down by fire are not themselves pure substances and therefore not elements.

[30]Perhaps Boyle is referring to such qualities as combustibility (commonly associated with sulfur) or fixity (commonly associated with salt). Some modern commentators are inclined to consider the alchemical principles (or the ancient elements for that matter) not as literal substances but as abstractions of qualities such as as these. (See, for example, Partington 1948.) Boyle, however, seems to say that these qualities are not perfectly embodied in any one substance, at least not in any substance which results from chemical analysis.

[31]Eleutherius summarizes the common features of analysis of several classes of materials, namely animal, vegetable, and mineral. The minerals (or inorganic substances) seem to be broken down into something like salt, sulfur, and mercury. The animal and vegetable (or organic) substances seem to be more complicated, yielding more substances upon analysis. The main components of organic materials seem to be salt, something volatile (i.e., readily evaporated, namely the "spirit"), and oil.

[32]Even though the results of the chemical analyses of the time are not exactly pure substances, still they are not as complicated as the composite bodies before analysis. So salt, earth, and the like may not be elementary, but it is useful to think of them as components of composite bodies.

[33]This is an interesting insight. Put in more modern terms, it says that medical activity in a composite substance is due to one of its components; therefore, administering only the active component would be a more effective treatment than administering the whole substance. Medically active components, however, tend to be chemical compounds, not elements; so the separation involved here is one of a composite body into its compounds, not a compound into its elements.

[34]Eleutherius suggests that the development of better analytical tools will be required before the question of elements can be resolved empirically; fire is simply too blunt an instrument. He was quite right on this score: improvements in the techniques of analytical chemistry markedly assisted the development of the science of chemistry, for new techniques often yielded new or more detailed information on chemical topics including the identification of elements.

[35]This speculation that it may be possible to break down substances so far as to be "useless" has been borne out by developments in the 20th century. The chemical elements recognized today are "elementary" for chemical purposes in that they persist in a recognizable form in chemical processes. But those elements can be broken down further into components, such as protons, neutrons, and electrons. This further analysis turned out to be enormously valuable in providing insight into chemical questions. (For instance, what distinguishes one element from another is the number of protons in its nucleus, and what happens in chemical reactions involves mainly the rearrangement of electrons.) Protons and neutrons are themselves composite particles; however, their structure, though important to the physical understanding of matter, is unlikely to have any applications to chemistry.

[36]In sum, Carneades believes that it is necessary to clear away faulty or unreliable chemical ideas before building a reliable system on a firm empirical foundation.

[37]So the dialogue concludes with the skeptical Carneades vowing to keep an open mind, and refusing to tip his (or Boyle's) hand on whether elements even exist or how probable he thinks Eleutherius' propositions.


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