Foundations of Chemistry

, Volume 14, Issue 3, pp 221–234

The ontological function of first-order and second-order corpuscles in the chemical philosophy of Robert Boyle: the redintegration of potassium nitrate


    • Department of Philosophy, AH 110Florida Atlantic University

DOI: 10.1007/s10698-012-9159-8

Cite this article as:
Banchetti-Robino, M.P. Found Chem (2012) 14: 221. doi:10.1007/s10698-012-9159-8


Although Boyle has been regarded as a champion of the seventeenth century Cartesian mechanical philosophy, I defend the position that Boyle’s views conciliate between a strictly mechanistic conception of fundamental matter and a non-reductionist conception of chemical qualities. In particular, I argue that this conciliation is evident in Boyle’s ontological distinction between fundamental corpuscles endowed with mechanistic properties and higher-level corpuscular concretions endowed with chemical properties. Some of these points have already been acknowledged by contemporary scholars, and I actively engage with their ideas in this paper. However I attempt to contribute to the debate over Boyle’s mechanical philosophy by arguing that Boyle’s writings suggest an emergentist, albeit still mechanistic, notion of chemical properties. I contrast Boyle’s views against those of strict reductionist mechanical philosophers, focusing on the famous debate with Spinoza over the redintegration of niter, and argue that Boyle’s complex chemical ontology provides a more satisfactory understanding of chemical phenomena than is provided by a strictly reductionist and Cartesian mechanical philosophy.




Historians and philosophers of science have generally regarded Boyle (1627–1691) as a key figure and champion of seventeenth century Cartesian mechanical philosophy. For example, Robert Kargon has emphatically stated that “[i]f Boyle’s theory of the structure of matter was essentially different from the existing mechanical philosophies [of his time], it still remains to be shown. The evidence … seems to indicate that Boyle’s ‘theory’ was at best a juxtaposition of Epicurean and Cartesian views” (Kargon 1964, p. 191). These historians of science often refer to the many writings in which Boyle explicitly extols the virtues of mechanism, in particular The Sceptical Chymist (1661) and The Excellency and Grounds of the Corpuscular or Mechanical Philosophy (1674), as evidence of Boyle’s faithful endorsement of Cartesian mechanism. Furthermore, although it is widely known that Boyle was himself a practicing alchemist who believed in the possibility of the ‘transmutation’ of metals, it is also agreed that Boyle attempted to understand transmutation in a way compatible with the mechanical philosophy.

This interpretation of Boyle’s corpuscular mechanical philosophy as strictly reductionist is reinforced in the work of, among others, Boas Hall (1952), Kuhn (1952) and, more recently, Klein (1994). In fact, in his essay ‘Robert Boyle and Structural Chemistry’, Kuhn write that “Boyle’s faith in the corpuscular principles of the ‘Mechanical Philosophy’ is the major source of his new emphasis in chemistry upon structure, configuration and motion” (1952, p. 19). These scholars are, however, not the first to attribute a strictly Cartesian mechanism to Boyle. In fact, according to Bernard Joly, this attribution can be traced at least as far back as Fontenelle who, in his History of the Royal Academy of Sciences (Histoire de l’Académie Royale des Sciences) of 1733, not only identifies corpuscularism with Cartesian mechanism but also attributes these undifferentiated positions to Boyle (Joly 2008). Joly explains that, after having opposed the ‘spirit of chemistry’ to the ‘spirit of physics’, “Fontenelle, in a manner that may seem rather abusive, effects a double operation. First, he identifies corpuscularism with Cartesian mechanism, in other words, with the idea that the explanation of all natural phenomena must be ‘reduced’ to the invocation of mechanical relations among ‘small particles’; there are, therefore, only two variables: the configuration of these small particles (their size and shape) and their motion. Secondly, he attributes this position to Boyle [Fontenelle effectue, d’une manière qui peut sembler abusive, une double opération. D’une part il identifie le corpuscularisme au mécanisme cartésien, c’est-à-dire à l’idée selon laquelle l’explication de tous les phénomènes naturels doit se « réduire » à l’invocation de relations mécaniques entre les « petits corps » ; il n’y a donc que deux variables : la configuration de ces petits corps (leur taille et leur figure) et leur mouvement. D’autre part il fait de cette position celle de Boyle]” (2008, p. 3). In fact, some eighteenth century chemists, such as Gabriel François Venel, went as far as regarding Boyle as more of a physicist than a chemist precisely because of his association with what they called ‘the corpuscularian-mechanical philosophy’. In his article on chemistry for Diderot and d’Alembert’s Encyclopédie, Venel says of Boyle that he “is ordinarily counted among the chemists, and he has indeed written much on chemistry. However, he is too much of a corpuscularian-mechanistic physicist or, strictly speaking, a physicist, so that we have contrasted him with the chemist at the beginning of this article [[Boyle] est ordinairement compté parmi les chimistes; & il a effectivement beaucoup écrit sur la chimie. Mais il est trop éxactement physicien corpusculaire-mécanicien, ou physicien proprement dit, tel que nous l’avons mis en contraste avec le chimiste au commencement de cet article]” (Venel 1796, p. 299). It is indeed the case that Boyle makes some very clear statements in favor of mechanism in several works, especially in The Excellency and Grounds of the Corpuscular or Mechanical Philosophy, the title of which clearly conflates the notion of corpuscularism with that of mechanism, as though these notions implied each other.1

However, despite the received view among historians of science up to the last stages of the twentieth century, a number of scholars have recently called into question the attribution of a strictly reductionist mechanical philosophy to Boyle.2 Boyle’s writings support this change in view as they clearly show that he distanced himself from the more extreme reductionist implications of Cartesian mechanism, particularly when it came to developing explanations for the results of his chemical experiments. In fact, Boyle rarely appealed directly to the mechanical affections of fundamental particles in his chemical explanations, he does not “reduce all chemical phenomena to the geometrico-mechanical affections of particles of inert matter” (Clericuzio 2000, p. 106), and he refrains from explaining “chemical phenomena by immediate and direct recourse to the mechanical affections of particles.”(Clericuzio 1990, p. 563). Boyle distinguishes between the strictly mechanical affections of fundamental corpuscles and the chemical properties of compounded corpuscles. For Boyle, although compounded corpuscles depend ontologically on fundamental particles whose properties are strictly mechanistic, the chemical properties of compounded corpuscles are both epistemically and explanatorily irreducible to the basic mechanistic properties of fundamental corpuscles. This ontological distinction allows Boyle to reconcile the mechanical corpuscularian philosophy with his experimental work. In fact, Boyle’s himself claims to be reconciling chemistry and Cartesian corpuscularism when, in the preface of A Physico-Chymical Essay, he explicitly expresses the hope that his experimental work.

may conduce to the Advancement of Natural Philosophy, if, as I said, I be so happy as, by any endeavours of mine, to possess both Chymists and Corpuscularians of the advantages that may redound to each Party by the Confederacy I am mediating between them, and excite them both to enquire more into one anothers Philosophy, by manifesting, that as many Chymical Experiments may be happily explicated by Corpuscularian Notions, so many of the Corpuscularian Notions may be commodiously either illustrated or confirmed by Chymical Experiments. (Boyle 2000c, p. 91)

To achieve this ‘mediating confederacy’ between chemistry and corpuscularian philosophy, Boyle focuses primarily on describing the chemical properties and processes that he encounters in his experimental work and on explaining these in terms of a corpuscularism that is mechanistic but not reductionist. In fact, Boyle distances himself from strictly reductionist philosophers like Spinoza who attempt to provide explanations for all chemical phenomena from a strictly Cartesian, mathematical, and a priori point of view. Ultimately, as a chemist and experimental natural philosopher, Boyle cannot bring himself to adopting such an unrelentingly reductionist position. Boyle makes this clear in An Essay of various Degrees or kinds of the Knowledge of natural things, when he states that Epicureans and Cartesians.

are so charm’d with ye clearness & pleasure of Theorys & explications, yt are deriv’d immediately from methaphisical and mathematical notions and & theorems; yt they oftentimes give forced and unnatural accounts of things, rather than not to be thought to have deriv’d them immediately from these highest principles. And, wch is much worse, they despise, & perhaps too condemn or censure all yt knowledge of the works of nature yt Physicians, Chymists & others pretend to, because they cannot be clearly deduc’d from the Atoms, or ye Catholick Laws of motion. (Boyle RSBP, folio 166r)

Several historians of science have already argued that Boyle distinguished between fundamental matter characterized by mechanistic properties and complex aggregations of corpuscles characterized by chemical properties.3 What I wish to contribute to this ongoing discussion of Boyle’s mechanical philosophy is the idea that Boyle may have held what we would call today an ‘emergentist’ conception of chemical properties. In fact, Boyle’s accounts of the origin of chemical properties suggest precisely such an emergentist, albeit still mechanistic, view.4 In this essay, I contrast Boyle’s views against those of strict reductionist mechanical philosophers, focusing in particular on the famous debate with Spinoza over the redintegration of niter. I defend the view that Boyle’s complex chemical ontology can be regarded as emergentist and that it provides a more satisfactory understanding of chemical phenomena than that provided by a strictly reductionist and Cartesian mechanical philosophy.

What is interesting about Boyle’s complex ontology is that it is not grounded on a simple dichotomy of reduction/emergence but is, rather, an adaptation of the mechanical philosophy to Boyle’s chemical work by reconciling a mechanistic conception of fundamental matter with a non-reductionist conception of chemical properties. In fact, this complex chemical ontology allows Boyle (1) to conceptualize more clearly the results obtained from his own chemical work, (2) to assert the autonomy of chemical explanations, in the context of chemical practice, over purely physical and reductionist explanations, and (3) to remain committed to a fundamentally mechanistic explanatory model.

The redintegration of potassium nitrate and the debate with Spinoza

Before expanding upon the details of Boyle’s chemical ontology, I will discuss an experiment that has become well-known in the literature on Boyle and the ensuing, and equally well-known, controversy that Boyle’s interpretation of this experiment generated with Baruch Spinoza. This experiment is the redintegration of potassium nitrate, and its significance for this essay is that this experiment illustrates Boyle’s commitment to chemical explanations and to the distinction between such explanations and those of strictly reductionist philosophers like Spinoza.

Boyle’s experiment with the redintegration of potassium nitrate, also called nitre or saltpeter, proceeds as follows. I quote below Boyle’s own account of this experiment at some length.

We took then common Nitre … and having by the usual way of Solution, Filtration, and Coagulation, reduc’d it into Crystals, we put four ounces of this purifi’d Nitre into a strong new Crucible in which … we melted it into a limpid Liquor, and whilst it was in fusion, cast into it a small live Coal, which presently kindled it, and made it boil and hiss, and flash for a pretty while: after which we cast in another glowing Coal, which made it fulminate afresh; and after that we cast in a third and a fourth, and so continu’d the operation till the Nitre would neither fulminate nor be kindled any more: after which we continu’d to keep it in a strong fire for above a quarter of an hour, that if any volatile part should yet remain, it might be forced off. Then taking out the Crucible, and breaking it whilst it was hot, we took out, as carefully as we could, the remaining fix’d Nitre before it had imbib’d much of the moisture of the air, and dividing it into two equal parts, we dissolved one of those portions in as much fair water as would just suffice for the solution of it, and then drop’d on it Spirit of Salt-petre till the ebullition occasion’d by the mutual action of those contrary Liquors did perfectly cease … The event of these Trials was, that the mixture wherein fair water was employ’d, did in a few hours fasten to the lower part of the sides of the Glass wherein it was put, some saline particles, which seem’d by their form … to be Salt-petre; … The Crystals were the next day taken out, being by that time grown somewhat greater, and more numerous, and disclos’d themselves, upon tryal, to be indeed Nitrous, as well by their manner of burning, as their shape. (Boyle 2000c, pp. 93–96)

After having thus analyzed the potassium nitrate into fixed niter and spirit of niter and resynthesized it into solid crystals of saltpeter, Boyle interprets the results of this experiment as follows.

when Salt-Petre is distill’d, the volatile liquor and fix’d Salt into which it is reduc’d by the fire, are endowed with properties exceeding different both from each other, and from those of the undissipated Concrete: for the Spirit of Nitre is (as we formerly have observ’d) a kind of Acetum Minerale, and possesses the Common qualities to be met with in acid spirits as such; whereas the fix’d Nitre is of an Alkalizate nature, and participates the qualities belonging generally to lixiviate Salts; and Salt-petre it self is a peculiar sort of Salt, discriminated by distinct properties both from those Salts that are eminently acid … and from those that are properly Alkalizate … And whereas Salt-Petre it self is partly fix’d, and partly volatile, the acid Ingredients of it are altogether volatile, the Alkalizate fix’d. (Boyle 2000c, pp. 105–106)

Boyle concludes from this that the parts constituting the saltpeter are of different specific and chemical natures, although made of the same universal matter as saltpeter itself. These constituent parts exhibit properties (alkalinity and fixedness for the fixed niter and acidity and volatility for the spirit of niter) that are different from those of the saltpeter. From the reconstitution of the saltpeter, however, Boyle concludes that saltpeter is not a mere mixture of different substances in which each ingredient retains its individual properties. Rather, saltpeter is a heterogeneous mixture in which the fundamental corpuscles of the components remain unchanged but the properties are chemically altered and transformed as a result of a structural change, or change in ‘texture’, during the process of synthesis. As Clericuzio points out, Boyle’s “explanation of the experiment [is] not grounded on the primary and mechanical affections of particles. His interpretation of the ‘redintegration’ of nitre [is] based on the consideration that nitre [is] a compound body and that the parts into which it was analyzed were not ‘volatile and fixed parts of that concrete’ but two distinct substances of different nature, which are obtained from nitre by altering its texture” (Clericuzio 2000, p. 140). “[W]hen the parts come to be dislocated, and the halituous and Alkalizate particles are enabled or made to disband from the Concrete, and associate themselves with those of their own nature, we see with how great an activity both the acid Spirit and the fix’d Salt are endow’d” (Boyle 2000c, p. 105).

Boyle’s interpretation of this experiment is philosophically interesting because he “does not so much invoke the movement and shape of corpuscles as he does the chemical qualities of the different substances that have the properties of dissolving, precipitating, or fixing [Boyle n’invoque pas tant le mouvement et la forme des corpuscules que les qualités chimiques des diverses substances qui on la propriété de dissoudre, de précipiter ou de fixer]” (Joly 2008, p. 4). Furthermore, and as will be discussed in more detail below, Boyle’s claims regarding the nature of the mixture and the alterations of the chemical properties of its components are evidence of a mechanical theory of matter that is not simplistically reductionist and may even suggest an emergentist conception of chemical properties.

Boyle’s interpretation of this experiment, as I have mentioned, generated some controversy and his attempt at explaining the results of the redintegration of nitre in non-reductionist terms met with criticism from several philosophers committed to Cartesian mechanical explanations. One of Boyle’s staunchest critics in this regard was the rationalist philosopher, Baruch Spinoza. More specifically, Spinoza rejects Boyle’s argument that the separation of the potassium nitrate is a decomposition of one distinctive chemical substance into two other chemical substances, and that the redintegration of the two separate chemical substances alters their chemical properties to transform them, once again, into potassium nitrate. Instead, Spinoza claims, the experiment is consistent with the Cartesian reductionist position that differentiations among extended substances are always due to different quantities of motion and rest. Spinoza argues that the different properties of the spirit of nitre and the fixed nitre are due to a difference in the motion of the fundamental particles, rather than to a difference of structure as Boyle surmises.

For Spinoza, Descartes’ a priori rationalistic approach to the theory of matter succeeds in uncovering the real nature of matter, and Spinoza does not believe that Boyle’s experiments with nitre either amplify or improve on Descartes’ work (Gabbey 1996, pp. 177–179). As well, for Spinoza, all aspects of and diversity in matter are accounted for by its fundamental mechanical properties. In his correspondence with Henry Oldenburg, Spinoza states that “Boyle infers from his experiments concerning the reconstitution of Niter that Niter is something heterogeneous, consisting of fixed and volatile parts, whose nature (so far as the Phenomena are concerned, at least) is nonetheless very different from the nature of the parts of which it is composed, though it arises solely form the mixture of these parts” (Curley 1985, pp. 173–174). However, Spinoza wishes to provide a different account and explains to Oldenburg that “[i]n order, then, to explain this phenomenon in the simplest possible way, I will posit no other distinction between spirit of nitre and nitre itself than that which is sufficiently manifest, namely, that the particles of the latter are in a state of rest, while those of the former agitate each other with no little vehemence” (Spinoza 2003, p. 86). In other words, Spinoza’s explanation entails the reduction of all phenomenal distinctions to the mechanical properties of fundamental particles.

Spinoza claims that the ‘fixed nitre’ (potassium carbonate) was actually an impurity mixed into the original sample of nitre (potassium nitrate), and that the spirit of nitre (nitric acid) was simply the volatile state of the pure, crystallized nitre portion of the original mix. The difference between spirit of nitre and the original sample of nitre was due to a difference in the motion of their particles, whose basic shape is the same, rather than to a difference in structure. For Spinoza, “[n]itre and the spirit of nitre [both] consist of rigid, carrot-shaped particles. [However] [t]he particles of nitre are at rest, those of spirit of nitre are in rapid motion; the fixed nitre slows the faster particles of the spirit of nitre to produce nitre, and it has pores whose size change and whose walls become brittle when the nitre is forced out by the fire. As for the difference in taste that Boyle noted between the fixed nitre (alkaline) and spirit of nitre (acidic), their particles lie lengthways on the tongue when slow, and prick it when they move fast” (Gabbey 1996, pp. 177–179). Therefore, for Spinoza, the ‘redintegration’ of nitre was the outcome of a mere mechanical association of particles in motion volatile particles (that is, particles in motion) with and fixed particles (that is, particles at rest).

Boyle’s reply to Spinoza’s critique is to argue that Spinoza insists on imposing an a priori Cartesian model on the experiment, rather than viewing the experiment as a way of adjudicating between alternative explanatory models. Although Boyle’s interpretation of the redintegration of nitre is no less theory driven than Spinoza’s, Boyle considers the experimental results of the redintegration of niter as a way of adjudicating between corpuscularism and the Peripatetic theory of substantial form. For Boyle, the experiment demonstrates that the Peripatetic view is mistaken since, if the substantial form of niter were destroyed in the analysis, the redintegration would not have been possible. Although Spinoza agrees with Boyle’s critique of the theory of substantial form, he begs to differ with Boyle’s chemical, rather than reductively mechanical, account of the reactions. Unlike Boyle, Spinoza’s interpretation is not only theory driven but driven by an a priori Cartesian framework that he does not consider to be amenable to refutation by any experimental result. For Spinoza, experiment “cannot uncover the nature of things: sensory knowledge belongs to the imagination, the knowledge of essences and causes to the intellect alone” (Gabbey 1996, p. 179). In order to disprove a conclusion that is dictated by reason itself, one would have to establish its impossibility experimentally, which is something that cannot be done. However, as long as it is possible to interpret results in a manner that is consistent with a theory determined by rational reflection alone, those results cannot weigh against a theory, although those experimental results that conform to a rationally determined theory do indeed confirm it. Since Boyle’s experiment with the redintegration of nitre did not establish the impossibility that the differences between substances are merely the result of differences among the mechanical properties of motion and rest of fundamental particles, there is no reason, according to Spinoza, to interpret this experiment in any other than a reductionist way. Generally, “[w]hile Spinoza [thinks] that he ha[s] explained the redintegration of niter only when he [has] reduced all chemical properties of niter and [its] components to geometrical and mechanical properties, Boyle account[s] for the redintegration on the grounds of the chemical properties of the corpuscles, and [does] not make any attempt to deduce them from [or reduce them to] the mechanical principles [of primary corpsucles]” (Clericuzio 1990, p. 577).

Although the experiment with nitre and the controversy it generated with Spinoza have been the focus of this discussion so far, one can also find evidence of Boyle’s preference for chemical, rather than reductively mechanical, explanations in the majority of his other experimental accounts. In the ExperimentalHistory of Colours, for example, Boyle explains his experiments with colors by relying solely on chemical properties of substances. In one particular experiment involving mercuric chloride, potassium hydrogen tartate, and sulphuric acid, Boyle explains the change of his solution from transparent, to orange, and back to transparent as occurring due to changes in the chemical properties of compound corpuscles, rather than a reduction to the mechanical properties of fundamental particles. Boyle justifies taking this approach on the ground that “[t]his … seems to be the Chymical reason of this Experiment, that is such a reason, as, supposing the truth of those Chymical Notions I have elsewhere I hope evinc’d, may give such an account of the Phœnomena as Chymical Notions can supply us with; but I both here and elsewhere make use of this way of speaking, to intimate that I am sufficiently aware of the difference betwixt a Chymical Explication of a Phœnomenon, and one that is truly Philosophical or Mechanical” (Boyle 2000f, p. 152).

The question at this point, then, is the following: How is Boyle able to reconcile his openly professed commitment to the mechanical philosophy with a conception of chemical properties as non-reducible and possibly emergent? The answer lies in the complex particulate theory of matter already referred to above and which I will discuss in detail at this point.

Boyle’s complex theory of matter and of chemical qualities

The debate over the fundamental nature of matter raged on in the seventeenth century among many natural and speculative philosophers, and Boyle’s rejection of reductively mechanical explanations for his experiments contributed importantly to this debate. Seventeenth century accounts of matter, including those found in textbooks, were usually theoretical and grounded in reductionist Cartesian mechanistic conceptions of fundamental particles. These accounts were deductively derived since, according to Cartesians, “deduction allowed finding general principles under which elements of knowledge were to be structured” (Smets 2008, p. 291) and these principles should be assumed and employed in order to interpret the results of chemical experiments. “Thus … there existed a real need, internal to chemistry itself, for a theory that gave a solid account of practice” (Smets 2008, p. 291). Boyle attempted precisely to develop such a theory that could both inform chemical explanations and account for the causal efficacy of chemical properties while remaining, ultimately, grounded in the mechanical philosophy. This theory of matter should, ultimately, be supported by experimental evidence, and Boyle’s various experimental writings purport to present such evidence.

As has already been stated in this essay and argued elsewhere by myself and other authors, corpuscularism does not entail a reductive mechanism and, especially in the sixteenth and seventeenth centuries, “the acceptance of a particulate theory of matter very rarely involved the idea that all natural phenomena could be accounted for by means of particles endowed only with mechanical properties” (Clericuzio 1990, pp. 563–564). Scholars have demonstrated that Boyle conceives of certain properties of matter, such as chemical qualities, as not reducible to strictly mechanical explanations. In fact, the majority of Boyle’s many defenses of the mechanical philosophy are not aimed at defending Cartesian reductionism but, rather, are primarily concerned with contrasting mechanism with the Paracelsian doctrine of the tria prima and of the Peripatetic notions of the four elements and of substantial form, which Boyle finds unacceptable. Boyle’s mechanical theory is an account of the properties of fundamental corpuscles but does not “entail that all chemical properties [are] reducible to … mechanical attributes [of fundamental particles]” (Clericuzio 1990, pp. 563–564).

To understand this aspect of Boyle’s approach, one must examine the details of his theory of matter. In his early manuscript titled “Of ye Atomicall Philosophy” (1651–1653), Boyle equates atoms, or fundamental corpuscles, with minima naturalia, that is, particles that are not further divisible. He states, “by Atoms … I understand not indivisible Mathematical points … but minima naturalia … because tho they may be further divided by Imagination yet they cannot by Nature” (Boyle, RSBP, folio 163r). In this essay, Boyle makes clear that he understands the fundamental properties of minima naturalia as strictly mechanical, that is, as shape, size, and motion. It is important to note, however, that Boyle’s theory of matter was not fully developed at this early stage and that it continued to evolve throughout his lifetime. With this in mind, however, I will present what I and other authors take to be his final position, based on the evidence of Boyle’s writings.

Through years of development, Boyle’s theory of matter becomes more complex and, in addition to adopting the notion of minima (or prima) naturalia as fundamental particles endowed with mechanical properties, he also embraces a version of the notion of seminal powers to explain chemical qualities though, for him, seminal powers are corpuscular in origin (Anstey 2002a). In order to explain the existence of corpuscular seminal powers, while at the same time maintaining a mechanistic notion of primary properties, Boyle classifies corpuscles into what we might call first-order and second-order corpuscles.5 First-order corpuscles, or minima naturalia, are the fundamental particles of matter that are described in terms of strictly mechanistic properties. Second-order corpuscles, on the other hand, are described as compounded corpuscles or primary concretions with chemical properties and seminal powers, that is, with specific powers to affect other parts of matter (Clericuzio 1990). Fragments of Boyle’s manuscripts clarify this classification of corpuscles, from lesser to greater and greater degrees of complexity. In one such fragment, he states: “I think it may be convenient to distinguish the Principles or more primitive, or simple Ingredients of mixt Bodys into three sorts, first primary concretions or coalitions [second-order corpuscles], next, secondary mixts, and thirdly, decompounded mixts, under which name I comprehend all sorts of mixt Bodys, that are of a more compounded Nature, than the Primary, or Secondary ones newly mentioned” (Boyle, RSBP, folio 41). This notion of compounded corpuscles was not new with Boyle, since it had already been adopted by other corpuscularians, such as Sennert, Basso, and Gassendi.

For Boyle, chemical properties are indeed less fundamental than mechanical properties. Yet, chemical properties must be taken into account in the context of experimental work and in order to explain experimental results. Both in his early works and in his later writings, “Boyle explains chemical reactions by means of corpuscles endowed with chemical properties … [In order to do this, he] resorts not to the ultimate blocks of matter [of the atomists], but to corpuscles of a higher order of composition” (Clericuzio 2000, p. 117). Boyle is also openly critical of the Epicureans and Cartesians who, in an a prioristic manner, “pretend to explicate every particular Phaenomenon by deducing it from the Mechanicall affections of Atomes or insensible particles” (Boyle RSBP, folio 166r). Thus, although Boyle argues that primary corpuscles are endowed with strictly mechanical affections, he does not believe that chemical reactions take place at the level of these ultimate, first-order corpuscles. Instead, “Boyle believed chemical reactions to take place between … corpuscles of a higher order. These higher-order corpuscles [are] differentiated primarily by means of their chemical characteristics, and not by the imposition of primary qualities [i.e., mechanical properties] on an undifferentiated first matter” (Newman 1996, p. 584).

Furthermore, the many remarks made by Boyle regarding the producibility or origin of chemical properties from ingredients that do not bear the properties in question before being compounded is evidence that Boyle may have endorsed a notion of chemical qualities as ‘emergent’ properties that cannot merely be reduced to shape, size, and motion of first-order corpuscles. In his essay on The Origin of Forms and Qualities, Boyle not only explicitly describes his complex classification of corpuscles but also gives indication that chemical properties originate from the various concretions of fundamental corpuscles. For Boyle, such chemical properties can be said to emerge from the ‘texture’ or structural composition of primary corpuscles. Boyle claims that

there are also Multitudes of Corpuscles, which are made up of the Coalition of several of the former Minima Naturalia; and whose Bulk is so small, and their Adhæsion so close and strict, that each of these little Primitive Concretions or Clusters (if I may so call them) of Particles is singly below the discernment of Sense, and though not/absolutely indivisible by Nature into the Prima Naturalia that compos’d it, or perhaps into other little Fragments, yet, for the reasons freshly intimated, they very rarely happen to be actually dissolv’d or broken, but remain entire in great variety of sensible Bodies, and under various forms or disguises. (Boyle 2000b, p. 326)

Second-order corpuscles, or primary concretions as Boyle calls them, are endowed with chemical qualities by virtue of the specific manner whereby the first-order corpuscles coalesce. This is the ‘texture’ or structural composition of compounded (second-order) corpuscles. According to Boyle, because fundamental matter “being in its own nature but one, the diversity we see in bodies must necessarily arise from somewhat else, than the matter they consist of” (Boyle 1991, p. 18). As he explains it, it is from the disposition of the second-order corpuscles,

that the Colour, Odour, Tast, and other qualities of that Body are to be deriv’d, it will be easie for us/to recollect, That such Changes cannot happen in a portion of Matter, without so much varying the Nature of it, that we need not deride the antient Atomists, for attempting to deduce the Generation and Corruption of Bodies from the fam’d σύγκρισιςκαìδιάκρισις, the Convention and Dissolution, and the Alterations of them, from the transposition of their (suppos’d) Atoms … And since, according to us, the various manner of the Coalition of several Corpuscles into one visible Body is enough to give them a peculiar Texture, and thereby fitt them to exhibit divers sensible Qualities, and to become a Body, sometimes of one Denomination, and sometimes of another. (Boyle 2000b, pp. 328–3310)

In Experiments and Notes About the Mechanical Origine and Production of Volatility, Boyle claims that “the same material parts of a portion of corporeal substance, which, when they were associated and contexed (whether by an Archeus, seed, form, or what else you please,) after such a determinate manner, constituted a solid and fixt body, as a Flint or a lump of Gold; by having their Texture dissolved, and (perhaps after being subtilized) by being freed from their former implications or firm cohesions, may become the parts of a fluid body totally Volatile” (Boyle 2000a, p. 432). Elsewhere, Boyle states that “what ever be the number or qualities of the Chymical Principles, if they be really existent in Nature, it may very possibly be shewn, that they may be made up of insensible Corpuscles of the determinate bulks and shapes [the first-order corpuscles]; and by the various Coalitions and Contextures of such Corpuscles [the second-order corpuscles], not only three or five, but many more material Ingredients, may be compos’d or made to result” (Boyle 2000d, p. 112) and “that the very Qualities of this or that Ingredient flow from its peculiar Texture” (Boyle 2000d, p. 114), that is, from the specific manner in which first-order corpuscles coalesce to form compounded corpuscles. Were the same first-order corpuscles to be arranged differently and form differently textured second-order corpuscles, the chemical qualities of the body in question would be different. In his essay on The Producibleness of Chymical Principles, Boyle examines the various chemical properties of salts and, regarding the property of salinity, he concludes that “whether we allow the Epicurean Hypothesis or the Cartesian; the first Saline Concretions that were produc’d by Nature must be confess’d to have been made of Atoms, or of Particles, that before their conjunction, were not Saline” (Boyle 2000e, p. 33), thereby implying that the property of salinity emerges from the conjunction and structural composition of these corpuscles.

Further along in the same essay, Boyle states that “a Disposition to be dissoluble in this or that liquor may be acquir’d by mixture and the new Texture of parts” (Boyle 2000e, p. 34). He then proceeds to give the examples of powdered sulphur and salt of tartar that, he claims, will not dissolve in spirit of wine. He notes, however, that “if this Salt and Sulphur be mixt together, spirit of Wine will in less than an hour and sometimes in less than a quarter of that time dissolve enough of this matter to be richly colour’d by it, and this without the help of external heat” (Boyle 2000e, p. 34). He concludes that the property of solubility of the sulphur and tartar in spirit of wine is a property that emerges from the compounding of sulphur and tartar, though it is not a property of the component parts. Further still, in this same essay, Boyle concurs with both Paracelsus and van Helmont that salts are producible from ingredients that are not salts, when he states that “upon the chymists supposition that in these mixt bodies there is both sulphur and mercury, besides a terra damnata, the same portions of matter, that pre-existed in the form of either of those simple ingredients must, by the operation of the fire, and an anomalous menstruum, have been turned into salt … we may safely conclude, that salt may be made of matter, that was not salt before, and consequently that salt may be de novo produced” (Boyle 2000e, p. 35). Boyle then devotes the rest of this essay to discussing specific experiments for the producibility of acid, volatile, and alkaline (or lixiviate) salts.

Returning to the redintegration of potassium nitrate, the essence of Boyle’s chemical interpretation of this experiment is that, if the parts were otherwise disposed and had a different compound texture, they would yield a compound body with different chemical properties from that of potassium nitrate. Thus, redintegration requires reassociation according to former (i.e., original) dispositions of fixed and volatile parts. Once again we see that, for Boyle, “the properties of compound corpuscles can be entirely different from those of the particles they are made of” (Clericuzio 2000, p. 124). It is the structural disposition or ‘texture’ of the particles that account for the emergence of chemical properties of corpuscular concretions that are not attributable to the mechanical properties of fundamental particles.

To the extent, therefore, that the same fundamental corpuscles can be compounded into different higher order concretions whose chemical properties depend upon the specific manner in which those corpuscles are compounded, it is clear that the chemical properties of a body cannot be deducible from or reducible to the mechanical properties of the individual first-order corpuscles. In fact, Boyle plainly states that “we can little better give an account of the Phænomena of many Bodies, by knowing what Ingredients compose them, than we can explain the Operations of a Watch, by knowing of how many and of what Metalls the Balance, the Wheels, the Chain, and other parts, are made” (Boyle 2000d, p. 111). Thus, the phenomena of dissolution, redintegration, volatility, fixedness and many other chemical phenomena witnessed in experiments cannot be explained simply by describing the mechanical properties of the fundamental particles of bodies.

We ought not to conclude from this discussion, however, that there is a divergence between Boyle’s mechanical philosophy and his experimental chemical work. Despite the arguments made to the contrary, Boyle’s reliance on chemical explanations in terms of the properties of corpuscular coalitions does not render him any less committed to the mechanical philosophy. His reliance on what we call ‘emergent’ chemical properties is, more than anything, evidence of his anti-reductionism than it is of any lack of commitment to the mechanical philosophy. Boyle remains firmly committed to the mechanical philosophy and to mechanical explanations, which he regards as the only and superior alternative to the theory of substantial form. For him, chemical properties originate from the textural arrangements of primary corpuscles, but ‘texture’ is considered a ‘mechanical affection’ because changes in texture are, for Boyle, changes in spatial relations. As Newman explains, “[instead of appealing to the size, shape, and motion of the uncompounded and initial particles, Boyle frequently based his mechanical explanations on the access, recess or transposition of unchanging [i.e., semipermanent] aggregate corpuscles with chemical properties. It does not follow from the fact that these explanations are not based on the catholic affections of the prima naturalia that they are not mechanical” (Newman 2006, p. 189). As Newman demonstrates, an understanding of Boyle’s explanations as non-mechanical is based on the erroneous assumption that mechanical explanations must reduce all phenomena to the catholic affections of fundamental particles. Newman, however, explains that

if we look at the vast majority of Boyle’s experimental demonstrations of the mechanical origin of qualities, it is precisely such aggregate corpuscles that usually come into discussion … These are aggregate corpuscles distinguished by their chymical properties, not initial atoms having primary qualities alone. Nonetheless, it is the ‘mechanical texture’ formed by the association of these finely ground particles that produces the explosiveness of gunpowder … The radical disjunction claimed by some scholars to exist between Boyle’s mechanical philosophy and chymistry is in fact illusory (Newman 2006, pp. 188–189)

Thus, one can argue that Boyle account of the origin of chemical qualities may be emergentist but also remains mechanical to the extent that chemical qualities emerge from the mechanical textural arrangements of compounded corpuscles. Boyle defends his adherence to the mechanical philosophy repeatedly, in fact, and states that “the mechanical principles are so universal, and therefore applicable to so many things, they are rather fitted to include, than necessitated to exclude, any other hypothesis, that is founded in nature, as far as it is so” (Boyle 2000d, p. 111).


As Gabbey explains, in the seventeenth century, “alleged experimental confirmations of mechanical hypotheses were far from being as conclusive as the theoreticians and experimentalists of the mechanical philosophy pretended” (Gabbey 1996, p. 180). At this time, “the chemical approach was pragmatic, realistic, and eclectic. The majority of chemists worked on real matter and real properties in a purposeful way … They simply could not afford to rely too closely upon a rigid theory” (Meinel 1988, p. 101). On the other hand, although mechanical theoreticians did not completely reject the role of experiment in establishing a theory of matter, Spinoza himself was intent on upholding the primacy of an a priori mechanistic ontology, and the resulting subordination of chemistry to physics, by forcing a strictly reductionist interpretation of experimental results that might, otherwise, suggest a different understanding of the complex nature of matter.

On the other hand, a practicing chemist such as Boyle used the mechanical philosophy to better understand the fundamental nature of matter but was not interested in turning to strictly reductionist explanations. The subordination of experimental chemical work to a strictly reductionist mechanical philosophy would result in “a sterile and occasionally adverse intellectual climate for an understanding of the processes underlying chemical change” (Kuhn 1952, p. 15). Boyle flexibly and pragmatically reconciled the mechanistic philosophy, which he considered far superior to the doctrine of substantial form, with the notion of irreducible chemical properties by embracing an ontology in which emergent chemical qualities are explained in terms of ‘textural’ arrangements which, although mechanical in nature, do not entail reduction to the primary properties of fundamental corpuscles. This ontology allowed Boyle to overcome the simplistic dichotomy of reduction/emergence, without having to negate his identity as a champion of the mechanical philosophy. “It is [also] clear that we can no longer accept the view that Boyle’s corpuscularism was simply a ‘physicist’s theory’ grafted by him onto a purely qualitative chemistry” (Newman 1996, p. 585).


Several authors have argued against the conflation of corpuscularism and mechanism, and further argument on this topic extends beyond the scope of this paper. For a more detailed, although not exhaustive, discussion of this topic, I refer the reader to Rattansi (1996), Clericuzio (1990, 2000), Pagel (2002), Debus (2002), and Banchetti-Robino (2011).


See, for example, Clericuzio (1990, 2000), Anstey (2000, 2002a), Chalmers (1993, 2009), Newman (1994, 1996, 2006, 2009a, b), and Newman and Principle (2002).


I refer the reader particularly to Clericuzio (2000), Anstey (2000, 2002a), Chalmers (2009), Newman (1994, 1996, 2006, 2009a, b), and Newman and Principle (2002). Although these scholars differ with regards to some of the conclusions that they reach with regards to Boyle’s relationship to the mechanical philosophy (either narrowly or broadly understood) and to the degree of Boyle’s commitment to reductionism at some level, these authors have forged new ground in the field of Boyle studies by moving scholarship away from the perspective of Boyle as being committed to a strictly reductionist and narrow conception of the mechanical philosophy and its application to chemical explanations.


The view that Boyle’s explanations remain mechanistic throughout his work, though they are not strictly reductionistic, has been argued convincingly and at length by Newman. This point has, in fact, been the subject of an extensive and lively debate between Anstey, Pyle, Chalmers, and Newman. See Anstey (2002b), Pyle (2002), Chalmers (2002, 2010, 2011), and Newman (2010). Though Chalmers and Clericuzio have argued for the existence of a dichotomy between Boyle’s mechanical philosophy and his experimental work, I will lean on the side of Anstey, Pyle, and Newman who take a more nuanced view of what the mechanical philosophy meant to Boyle and how it informed his chemical experiments and his explanations of chemical phenomena. Newman, in particular, points out that Clericuzio and Chalmers base their arguments on a narrow understanding of the mechanical philosophy, one that conflates mechanism with strict reductionism. Although Cartesian mechanism was indeed reductionistic, Newman convincingly argues that there are iterations of the mechanical philosophy that do not entail strict reductionism. Through a careful analysis of Boyle’s writings, Newman demonstrates that Boyle’s mechanical philosophy constitutes one such iteration and, as such, is not at odds with his experimental work or his chemical explanations.


This is not Boyle’s own terminology but is attributable, instead, to Clericuzio. I adopt the same terminology for the sake of convenience though, as mentioned in an earlier note, I ultimately disagree with some of Clericuzio’s conclusions regarding the dichotomy between Boyle’s mechanical and his experimental work and chemical explanations.


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