Foundations of Chemistry

, Volume 13, Issue 3, pp 173–186

Ontological tensions in sixteenth and seventeenth century chemistry: between mechanism and vitalism


    • Department of PhilosophyFlorida Atlantic University

DOI: 10.1007/s10698-011-9126-9

Cite this article as:
Banchetti-Robino, M.P. Found Chem (2011) 13: 173. doi:10.1007/s10698-011-9126-9


The sixteenth and seventeenth centuries marks a period of transition between the vitalistic ontology that had dominated Renaissance natural philosophy and the Early Modern mechanistic paradigm endorsed by, among others, the Cartesians and Newtonians. This paper will focus on how the tensions between vitalism and mechanism played themselves out in the context of sixteenth and seventeenth century chemistry and chemical philosophy, particularly in the works of Paracelsus, Jan Baptista Van Helmont, Robert Fludd, and Robert Boyle. Rather than argue that these natural philosophers each embraced either fully vitalistic or fully mechanistic ontologies, I hope to demonstrate that these thinkers adhered to complicated and nuanced ontologies that cannot be described in either purely vitalistic or purely mechanistic terms. A central feature of my argument is the claim that a corpuscularian theory of matter does not entail a strictly mechanistic and reductionistic account of chemical properties. I also argue that what marks the shift from pre-modern vitalistic chemical philosophy to the modern chemical philosophy that marked the Chemical Revolution is not the victory of mechanism and reductionism in chemistry but, rather, the shift to a physicalistic and naturalistic account of chemical properties and vital spirits.


Chemical philosophyAlchemyVitalismMechanismParacelsusVan HelmontBoyle


The sixteenth and seventeenth centuries marked a period of transition between the vitalistic ontology that had dominated Renaissance natural philosophy and the early modern mechanistic paradigm that was endorsed by Cartesian natural philosophers, among others. However, even with the dawning of the eighteenth century Chemical Revolution, chemistry remained resistant to the mechanical philosophy. What one discovers, when examining the chemical philosophies of the sixteenth and seventeenth centuries, is that these transitional philosophies involved quite complex and nuanced ontologies that cannot be easily classified as either strictly vitalistic or strictly mechanistic. In fact, in many of the most important chemical theories of this period, vitalism coexisted quite comfortably with corpuscularian theories of matter. More than this, one also discovers that, to the extent that chemical philosophy resisted subsumption under the mechanical philosophy, it was not the supplanting of vitalism by mechanism that ushered in the Chemical Revolution. Rather, this revolution in chemistry was brought about by a naturalized and physicalistic, although non-mechanistic, interpretation of chemical qualities and operations and of the notion of vital spirit.

This paper will examine these ideas by focusing on a few of the more significant transitional chemical philosophies of the sixteenth and seventeenth centuries, in order to show how chemical philosophers at this time adhered to complicated ontologies that only slowly and gradually shifted from a vitalistic point of view to a naturalistic and physicalistic, albeit non-mechanistic, account of chemical qualities and operations. For the sake of brevity, I will restrict my discussion to the chemical philosophies of Sebastien Basso, Jan Bapstista van Helmont, and Robert Boyle. I will also examine the work of Paracelsus, since his chemical philosophy provides the background for the work of Basso, van Helmont, and Boyle. The role played by these chemical philosophies in the shift from vitalism to physicalism is best understood when one focuses on their theories of matter and of vital spirits, and on how the changes in how these notions were conceived ultimately ushered in the Chemical Revolution.

Vitalism in Paracelsus, van Helmont, and Basso

Vitalism has been generally regarded as the view that claims that ‘vital forces’ or ‘vital spirits’ are causally operative in nature, and that the presence of ‘vital force’ or ‘vital spirit’ marks the difference between organic and inorganic matter. Vitalistic descriptions of natural phenomena tend to be qualitative, and vitalistic processes tend to be viewed as holistic and teleological. Most importantly for this essay, vitalism views the causes of motion as inherent within matter and treats all of nature “as if it were intrinsically active and self-organizing” (Stehr and Meja 2005, p. 77). Throughout the history of both speculative and natural philosophy, vitalistic theories have often been overlaid with theological overtones of one sort or another, and the vitalistic theories discussed herein are no exception. Renaissance and early modern natural philosophers believed that they lived in an enchanted universe, that the physical universe did not consist of inert matter but either was itself animate (i.e., it contained a ‘world soul’ or anima mundi) or was inhabited by vital forces and spirits that played a causal role in the occurrence of natural phenomena. For these philosophers, the presence of a world soul or of vital forces and spirits was ultimately attributed either to divine emanation or to divine action. Another characteristic of Renaissance vitalism was that it affirmed a fundamental correspondence between what is above, the macrocosm, and what is below, the microcosm. “The theory of a correspondence between microcosm and macrocosm was at the center of a group of ideas derived from the […] mystical-alchemical tradition crossed with themes common to Neoplatonic mysticism. The vital substances of objects [were] made up of invisible spirits or forces of nature” (Rossi 2001, p. 141). Natural philosophers, or natural magicians as they were called in the Renaissance, were individuals who not only studied these vital forces and correspondences but also learned how to deploy them for the purpose of controlling or altering natural phenomena. Vitalism dominated natural philosophy during the fifteenth and sixteenth centuries as a result of the Neoplatonic and hermetic traditions that informed Renaissance culture. It infused the work of such thinkers as Marsilio Ficino, Tommaso Campanella, Cornelius Agrippa, and Giordano Bruno and continued to dominate natural philosophy well into the seventeenth century.

One discipline within the Renaissance tradition of natural magic that was especially receptive to the vitalistic ontology of Neoplatonism was alchemy and, even during the transition from alchemy to modern chemistry, lingering elements of the vitalistic standpoint continued to resonate within chemical philosophy. As well, to the extent that chemical philosophy impacted on developments in iatrochemistry (i.e., pharmaceutical chemistry) and medicine, vitalism continued to also impact these disciplines throughout the seventeenth and part of the eighteenth century. However, one of the misconceptions informing much of the literature on this subject is that vitalism ended with the advent of corpuscular philosophy and atomism. At the heart of this misconception is the belief that corpuscularism implies mechanism and that, therefore, the advent of the corpuscular philosophy is responsible for sealing the lid on the casket of vitalistic theories. However, this is indeed a misconception. The historical process whereby ancient corpuscularism and atomism were revived in the sixteenth century is, in fact, quite complex. Although, the atomism of Democritus and Leucippus was physicalistic and mechanistic, what made it possible for particulate matter theory to be resurrected after millennia was the survival, through late antiquity, the middle Ages, and the Renaissance, of the ancient notions of minima naturalia and of non-physical semina rerum. Several medieval and Renaissance theories employed the notion of minima naturalia as the smallest possible particles in nature, not further reducible to other particles. By interpreting the notion of minima naturalia as minimum-sized particles of reagents, many Medieval and Renaissance alchemists developed their own type of corpuscularism or particulate matter theory, called ‘alchemical atomism’, as a qualitative version of atomism. The Neoplatonic notion of semina rerum also played a significant role in the revival of atomism in the sixteenth century for, although the semina were interpreted in the Plotinian and Augustian traditions as spiritual archetypes in nature, semina were understood by corpuscularians of the late seventeenth century in much more physicalistic terms. Although,“[m]ost historians [and philosophers] of science have considered early seventeenth-century atomism as preparatory to the mechanical theory of matter” (Clericuzio 2000, p. 37), there is strong evidence to show that, for much of the seventeenth century, chemical philosophers adopted a view of matter that was both corpuscular and vitalistic. In other words, these chemical philosophers adhered to a particulate matter theory while also embracing the idea that chemical qualities and operations were non-mechanistic and involved the action of vital spirits and ferments. “The Neoplatonic spirit of the world [anima mundi] was widely adopted by chemical philosophers as a principle of motion and life. In a hierarchically organised universe it was deemed to be a substance originating in the stars and therefore superior to the four elements. This notion became central to chemistry and medicine thanks to [Marsilio] Ficino’s De vita Philosophicae (1571)” (Clericuzio 2000, p. 37).

In order to understand the complex ontologies that informed the chemical philosophy of the sixteenth and seventeenth centuries, one must understand that chemical philosophy had been involved in a process of self-definition and development since it was first articulated as such in the work of the controversial alchemist Paracelsus. Thus, a clarification of the context in which sixteenth and seventeenth century chemistry evolved is in order. Chemistry, as a discipline, does not enjoy the same kind of long historical tradition that is enjoyed by astronomy, mechanics, mathematics, and physics. In fact, up to the sixteenth century, chemistry “had no organized structure whatsoever, no theories of change and reactions, and no clearly defined tradition. Like geology and magnetism, chemistry became a science between the seventeenth and eighteenth centuries. Unlike mathematics, mechanics, and astronomy, it was itself a product of the Scientific Revolution” (Rossi 2001, p. 137). As Rossi (2001, p. 139) tells us, “[t]here is no figure like a Euclid, Archimedes, or Ptolemy in the history of chemistry. Instead, modern chemists find themselves in the somewhat disconcerting company of alchemists, druggists, iatrochemists, sorcerers, astrologers, and other sundry figures.” One of the reasons why chemistry was long considered to be the red-headed stepchild in the family of science is that, for much of its history up to the sixteenth century, it was primarily a practical enterprise that did not seem to be anchored upon a solid theoretical and philosophical foundation. The scientific status of chemistry was, therefore, dependent upon the development of a chemical philosophy and, as surprising as it may seem, the person responsible for developing the first genuine chemical philosophy is the infamous alchemist known as Paracelsus.

Despite his legendary fame as a bombastic alchemist and occultist, Theophrastus von Hohenheim, a.k.a. Paracelsus, (ca. 1493–1531) was a seminal figure of early chemistry. Most importantly, Paracelsus helped to transform sixteenth century alchemy by giving it an essentially medical identity, and he made this the basis for the development of an alchemical epistemology (Rattansi and Clericuzio 1994). Paracelsus made significant advances in medicine by arguing against the Galenic and Scholastic view that disease was caused by an imbalance of the four bodily humors, which might be cured by bleeding or herbal remedies, and by claiming instead that disease was caused by the presence of external agents attacking the body and this could be cured through ‘chemical’ remedies. He identified the characteristics of many illnesses, such as goiter and syphilis, and treated them with sulphur and mercury compounds. He was, therefore, “the first to introduce the medicinal use of mineral substances to the practice of medicine. Chemistry, or the spagyric art, became the cornerstone of medicine” (Rossi 2001, p. 142). By all accounts, however, the characterization of Paracelsus as an alchemist and mystic is not a mistaken one. He fits very well within the Renaissance tradition of natural philosophy and natural magic to the extent that the theoretical framework upon which his work relies is staunchly vitalistic and not only posits the existence of vital forces and spirits but also fully affirms the theory of correspondence between microcosm and macrocosm. Paracelsus’s vitalism is, not surprisingly, theological and it shapes his chemical interpretation of Genesis, in which creation is understood as a separation of the elements by God. For Paracelsus, “[s]ince the divine creation [is] best understood as a chemical process, then nature must continue to operate in chemical terms. Chemistry [is] the key to nature—all created nature” (Debus 2002, p. 86).

Paracelsus’s chemical philosophy was based upon three fundamental principles: His theory of prime matter, his theory of elements, and his theory of principles. His theory of prime matter, as previously stated, was based upon his chemical interpretation of Genesis in which God is a divine chemist who spontaneously created the world ex nihilo (Rossi 2001). Paracelsus’s theory of the elements included prime matter (i.e., water) and fire, earth, and air, which were also considered matrices. “Plants, minerals, metals, and animals were the fruit of the four elements” (Rossi 2001, p. 141). Although, Paracelsus inherits his theories of prime matter and of the elements from ancient sources, it is with his theory of principles that he makes a truly original contribution to alchemy and to chemical philosophy. The principles of chemical reaction, according to Paracelsus, are salt, sulfur, and mercury, what he calls the tria prima. “This tria prima also consist[s] of spiritual substances and correspond[s] to the Body, Soul, and the Spirit. Salt makes bodies solid, Mercury makes them fluid, and Sulfur makes them inflammable” (Rossi 2001, p. 141).

Although, the theory of the tria prima was a modification of earlier sulfur-mercury theories of metals, it has a special significance in the rise of modern science because it represents a broadening of these theories “to provide an explanation for all nature” (Debus 2002, pp. 78–79). For Paracelsus and for later Paracelsian, vital spirit is essential for both the organic and the inorganic worlds. “Spirits were conceived as the active agents, upon which all the principal operations in nature and in the human body depended” (Clericuzio 1994, p. 52). In his De Natura Rerum (1537), Paracelsus states that “[t]he life of things is none other than a spiritual essence, an invisible and impalpable thing, a spirit and a spiritual thing. On this account there is nothing corporeal, but has latent within itself a spirit and life, which, as just now said, is none other than a spiritual thing.”1

Paracelsus’s chemical philosophy, however, was not merely mystical but also contained the fundamental elements of what would later become modern chemistry and modern scientific method. Paracelsus’s approach, for example, was solidly empirical. According to Paracelsus, “to attain true knowledge one must abandon the surface of bodies, penetrate their inner nature and break them up into their constituent parts until each of these is accessible to sight and touch” (Bianchi 1994, p. 18). To make the constituent parts of bodies accessible to the alchemist, Paracelsus emphasized analysis. However, he “and his followers laid the foundations for viewing analysis as only half of the equation—as a necessary preliminary to resynthesis” (Newman and Principe 2005, p. 79). Paracelsus and his followers thus changed the practice of alchemy by emphasizing the twin processes of analysis and synthesis (spagyria), to allow them to penetrate the true inner nature of bodies. When discussing the inner nature of bodies, Paracelsus was influenced by Ficino and “placed special emphasis on semina [or semina rerum], which he considered as invisible spiritual forces and as archetypes” (Clericuzio 2000, p. 18). There are clearly echoes here of the Augustinian doctrine of seminal reasons in Paracelsus’s conception of semina. “[S]emina, which originate in the Word [or Logos] are contained in the Yliaster [the universal matrix of the cosmos] and are prior to chemical principles and to elements. Nature as a whole is a panspermia” (Clericuzio 2000, p. 18), that is, the seeds of life imbue the entire universe. The notion that semina are responsible for the generation of natural bodies, including metals in the bowels of the earth, continued to influence Paracelsian chemical philosophers throughout the sixteenth and much of the seventeenth century. Paracelsus’s contemporary, Girolamo Fracastoro, took this Neoplatonic notion of semina rerum a step further by combining it with Lucretian atomism and reinterpreting it “in terms of invisible units of matter” (Clericuzio 2000, p. 17) and arguing that semina are also the causes of communicable diseases, when they propagate through the atmosphere and penetrate a host organism. In this way, both Fracastoro and Paracelsus greatly advanced the medical theory of disease by moving away from a strictly Galenic theory of humoral imbalance and toward the ontological theory of pathology and contagion.

The notion of semina rerum continued to influence many sixteenth and seventeenth century Paracelsian who embraced both a vitalistic ontology and a corpuscular and, more specifically, atomistic conception of matter. One of the seventeenth century Paracelsian whose work is particularly intriguing is Sebastien Basso (also known as Basson or Bassonus). Basso’s Paracelsian chemical philosophy, which he developed in his Philosophia Naturalis (1621), “stands out as one of the earliest and most articulate expositions of the corpuscular theory of matter” (Clericuzio 2000, p. 39). In fact, along with Isaac Beeckman, Sebastien Basso is considered to be one of the inventors of molecular theory. Yet, Basso’s work also stands out as a prime example of Neoplatonic vitalism. By motion, for example, Basso is referring to sympathy and antipathy, that is, to attraction and repulsion, and he attributes the motions of atoms not to external and mechanistic laws but to the actions of the world soul and, ultimately, of God. We, thus, find in Basso a strong affirmation that all natural phenomena are caused by the motions and rearrangements of atoms and, in that regards, he has much in common with later mechanistic atomists. But what distinguishes his views from those of later atomists and materialist corpuscularians is that, for him, this motion must be attributed to vital spirit, and vital spirit is to be understood in non-material and non-mechanistic terms. Although, Basso’s movement toward a corpuscularian theory of matter is a significant contribution to the eventual development of modern chemistry, other Paracelsian, such as Petrus Severinus, took even further steps towards the development of a theory of vital spirits that would, ultimately, lead to the late seventeenth century reinterpretation of these spirits in physicalistic terms.

We, therefore, find that, at the end of the sixteenth and the beginning of the seventeenth century, the chemical interpretation of vital spirit becomes unambiguously chemical, while still retaining a strong Neoplatonic tone. For example, the work of Duschesne and Croll develops the view “that medical spirits and spirits extracted by chemists [have] the same source, namely, the spirit of the world. On this basis they stated that the only active remedies [are] those prepared by using spirits extracted by distillation” (Clericuzio 1994, p. 53). Such an unambiguous chemical interpretation of vital spirit is even more evident in the chemical philosophy of Jan Baptista van Helmont (1579–1644). For van Helmont, vital spirit (Archeus) is conceived as an alkaline volatile salt that moves through the body. Van Helmont states that “[t]he spirit of life receives in the left ventricle of the heart a ‘divine illumination’, by which it is enabled to preserve and to sustain life […] within the left ventricle of the heart, vital spirit is generated from the volatile salt contained in cruor [blood without spirit] and by means of a local ferment” (Clericuzio 1994, p. 53). Van Helmont theory of spirit, however, still retains a strong Neoplatonic tone, although he rejects certain aspects of Neoplatonic thought such as, for example, the traditional analogy between microcosm and macrocosm.

We find that van Helmont develops an interesting hybrid theory that combines corpuscular and quasi-physicalistic explanations of many chemical phenomena with aspects of Paracelsian vitalism. Unlike other natural philosophers before him who had embraced either a notion of minima naturalia or of semina rerum, van Helmont’s chemical philosophy embraces both of these notions. However, unlike Frascastoro, van Helmont follows Paracelsus in interpreting semina rerum as “the main agents in nature [and as] spiritual, non-corporeal entities” (Clericuzio 2000, p. 56). For van Helmont, the minima naturalia are interpreted in strictly physical terms as corpuscles. In fact, “Helmontian atoms are identical with the minima naturalia, i.e., the smallest particles into which a substance may be divided. There is little doubt that for van Helmont minima naturalia are actual physical units. [However,] [i]t is also apparent that they have qualitative determinations, not mechanical properties” (Clericuzio 2000, p. 56). Non-mechanical properties are accounted for by the semina rerum, which work with the minima naturalia to bring about changes in nature by providing the spiritual force of action that brings about qualitative chemical alterations. Van Helmont claims that, in order to provide a mechanical explanation for chemical alterations such as, for example, the mixture of substances, one would have to restrict oneself to explaining this phenomenon by considering only the mechanical properties of shape, size, and motion. Therefore, under such a mechanistic model, a mixture of substances would have to be explained as the juxtaposition of physical parts. However, according to van Helmont, a “purely mechanical juxtaposition of [physical] parts does not bring about a real mixture [of substances]” (Clericuzio 2000, pp. 58–59). It does not bring about a true synthesis. This is why mechanical principles cannot explain chemical reactions. Instead, van Helmont claims that chemical reactions, mixtures of substances, and transmutations depend upon ferments that are contained in semina rerum, which are the formative principles from which all natural bodies originate. These ferments are themselves formative spiritual agents and, although analysis and “reduction of bodies into their minimae partes is a ‘pre-condition’ for transmutation—[it] is ultimately a spiritual process” (Clericuzio 2000, p. 60).

Van Helmont explains many physical changes in this manner, changes such as the production of a gas for example, and interprets these as changes in “the disposition of the tria prima within the corpuscles of water […] The purely material change, that is the attenuation of water parts into atoms, is preliminary to a process that is qualitative, not mechanical” (Clericuzio 2000, pp. 57–58). Therefore, physical change takes place in the minima naturalia, but the process of chemical change that ensues is the action of semina rerum. With this nuanced ontology, van Helmont makes significant contributions to the development of modern corpuscularian theory such as, for example, his explanation of certain chemical reactions, such as the “transmutation” of iron into copper and the production of glass, in corpuscular terms (Clericuzio 2000). “Both [chemical reactions] are explained in terms of addition and subtraction of particles. The notion of atoms is also employed in van Helmont’s theory of mixture and of generation […] [But] [t]hese corpuscular views by no means presuppose a mechanical theory of matter […] [Van Helmont] imposed severe restrictions on the corpuscular theory of matter. Semina rerum and ferments are the active principles on which all natural phenomena ultimately depend” (Clericuzio 2000, pp. 58–61).

Cartesian mechanism and the ‘chemistry’ of Robert Boyle

In order to understand the reasons why many chemical philosophers of the sixteenth and seventeenth centuries rejected mechanical explanations of chemical phenomena, one must first understand what the mechanical philosophy implied. ‘Mechanism’, or the mechanical philosophy, is the view “according to which matter is inert and all interactions in nature are produced by the impact of particles” (Clericuzio 2000, p. 7). In this sense, Cartesian mechanism is also reductionistic, that is, all qualities (including chemical qualities and reactions) are thought to be reducible to the mechanical and quantitative properties of shape, size, and motion. For reductionists, all higher-level phenomena and properties are entirely deducible from lower-level properties. In this view, “the physical world is represented by particles of matter in motion and can be interpreted by the laws of motion determined by statistics […] dynamics [and] mechanics […] Natural phenomena such as air resistance, friction, the different behaviors of individual bodies, the qualitative features of the physical world were now considered irrelevant to the discourse of natural philosophy or viewed as disturbing circumstances which were not […] to be taken into account in an explanation of the physical world” (Rossi 2001, p. 122).

For Descartes and for the Cartesian mechanists, “any explanation of natural events requires the building of a mechanical model as a ‘substitute’ for the actual phenomena being studied” (Rossi 2001, p. 125). Mechanical philosophy is, therefore, anti-vitalistic and anti-teleological, since it assumes that “nature is not the manifestation of a living principle but is a system of matter in motion that follows [mathematically precise] laws […] the explanation of natural phenomena excludes all reference to vital forces or final causes” (Rossi 2001, p. 125). With regard to the application of the mechanistic philosophy to chemistry, “Descartes proposes to explain the properties of chemical substances by invoking the configuration of the “small particles” of which they are formed; with regard to chemical operations, one can hypothesize that they result from the manner in which those small particles come into contact with one another through the incessant movement in which they have been agitated by the flux of subtle matter [Descartes propose de rendre compte des propriétés des substances chimiques en invoquant la configuration des «petites parties» dont elles sont formées; quant aux opérations de la chimie, on peut faire l’hypothèse qu’elles résultent de la manière dont ces petites parties entrent en contact avec les autres dans the mouvement incessant dont elles sont agitées par les flux de la matière subtile]” (Joly 2008).

Although, Descartes himself never sets out the principles of a “Cartesian chemistry” as such, in the fourth part of his Principles of Philosophy (Les Principes de la Philosophie) of 1647, he discusses both the subject matter and the operations of chemistry. For example, his account of how different metals form in the earth is exclusively in terms of the shapes and sizes of the corpuscles that compose the different metals: “According to the different sizes and shapes of these particles of matter […], they compose the different kinds of metals, which I would have here explained in greater detail had I had the convenience to conduct all of the experiments that would be required to verify my reasoning on this subject [selon les diverses grandeurs et figures qu’ont ces parties du corps […], elles composent diverse espèces de métaux, lesquelles j’aurais peut-être ici plus particulièrement expliquées si j’avais eu la commodité de faire toutes les expériences qui sont requises pour vérifier les raisonnements que j’ai faits sur ce sujet]” (Descartes 1973, pp. 399–400). In Principles of Philosophy, Descartes also attempts to give mechanistic and reductionist accounts of all properties of matter, including chemical properties and properties such as magnetism, and of chemical operations such as distillation, which he explains as the forced escape of small particles from the pores of material bodies by means of fire and the rejoining of those escaped particles by means of an alembic. In his view, “the particles that can be easily chassed out of terrestrial bodies by the action of fire are of different types, as one can experience quite easily through chemistry […] there are those […] that escape quite easily from those bodies; that is to say, those that, being collected and joined together through the means of an alembic, compose the aqua vitae, such as we are accustomed in extracting from wine, from wheat and from numerous other materials [les parties qui peuvent être chassées hors des corps terrestres par l’action du feu sont de divers genres, comme on expérimente fort clairement par la chimie […] il y en a […] qui sortent fort aisément hors de ces corps; à savoir celles qui, étant ramassées et jointes ensemble part le moyen d’un alambic, composent des eaux-de-vie, telles qu’on a coutume de les tirer du vin, du blé et de quantité d’autres matières]” (Descartes 1973, p. 441).

In addition to accounting for all the properties of matter in terms of the shape and size of its particles, the Cartesian mechanical philosophy accounts for all changes in inorganic and organic material bodies through deterministic and mechanistic laws of motion that are external to matter itself. According to this view, “all interactions in nature are produced by the impact of particles” (Clericuzio 2000, p. 7) in accordance with mechanical principles. For mechanists, matter is not intrinsically active or self-organizing and its motions are not self-determined. Instead, its motions are entirely determined by mechanistic causal chains and external laws of motion. For dualistic mechanists like Descartes, although matter itself is not active or self-determined, self-determination exists in the world to the extent that minds exist and are active and self-determined. For materialist mechanists like La Mettrie, on the other hand, since only inert matter exists, there is no such thing as self-organization or self-determination in the world.

This view, however, was not dominant in the context of seventeenth century chemistry, physiology, and medicine. In fact, for many chemists and physiologists, organization and spirit were inherent in matter, although in this period of transition, spirit was interpreted in chemical terms. “[F]rom the 1650s the notions of spirit (and of fermentation) became central issues […] [many English chemists and physiologists] shared the view that matter was endowed with an internal principle of organization, life and sensibility, namely, the spirit, which they described in terms of particles having specific chemical properties” (Clericuzio 1994, p. 59). This explains why “the distillation of spirits became an important component of seventeenth-century chemistry and medicine […] [for the purpose of] identifying and manipulating the spiritual essences extracted from natural bodies by means of distillation […] [and for] ‘capturing’ the spirit of the world, which Paracelsian conceived as the celestial vital substance contained in the air” (Clericuzio 1994, pp. 53–54).

Paracelsus had identified his celestial vital substance, or anima mundi, as the aerial niter (also called saltpeter, i.e., potassium nitrate). His reason for identifying the vital spirit with saltpeter is that potassium nitrate gives off life-sustaining oxygen when heated. Paracelsus had already reflected on what he considered to be the unique properties of saltpeter and had claimed that “no other salt in the world is like [saltpeter] […] The part played by Saltpeter in gunpowder is one reason why it is different from all other salts, and Paracelsus repeatedly explained thunder and lightning in terms of an aerial, windy, or aetherial nitre and sulphur” (Debus 1964, p. 47). Paracelsian later contended that, in addition to salt, there were two volatile parts in saltpeter, sulphur and mercury, which were, respectively the soul and the spirit of the aerial nitre. Based upon Paracelsus’s own investigations into the nature of the aerial nitre and upon the Neoplatonic belief in the microcosm/macrocosm analogy, the Paracelsian developed the theory that the vital spirit originates in the celestial sphere and is carried in the air. It is then inhaled by human beings and reaches the heart, from which it is “carried around the body in a circular motion, imitating the divine circularity [of the celestial bodies]. This motion impressed on the blood relates not only to the spirit of the blood in the heart but to all of the spirit of the blood in the body” (Debus 2002, p. 235). There is, therefore, throughout the work of the Paracelsian, a persistent interest in the blood and its relation to the vital spirit. Like van Helmont’s identification of vital spirit with volatile alkaline salt, the Paracelsian’ identification of anima mundi with saltpeter and their identification of aerial nitre as something that penetrated the body through the blood were important steps toward the late seventeenth century naturalization of the notion of vital spirit and the reinterpretation of this notion in physicalistic terms.

It is with this context in mind that I now turn to the work of another transitional figure in chemical philosophy, Robert Boyle (1627–1691). Boyle has generally been regarded by most historians of science as one of the principal champions of mechanism in the seventeenth century and as a key figure in advancing the Cartesian mechanical philosophy. Historians of science point to the many writings in which Boyle extolled the virtues of the mechanical philosophy and to his work, The Sceptical Chymist, in which Boyle responds to and critiques aspects of spagyrical and alchemical philosophy. Although, it is widely known that he was himself a practicing alchemist who believed in the possibility of the ‘transmutation’ of metals, it is also the case that Boyle attempted to understand transmutation in a way compatible with the mechanical philosophy. Aside from Boyle’s own claims in favor of the mechanical philosophy, historians of science also point to his corpuscular conception of matter as further evidence of his commitment to mechanism.

This interpretation of Boyle’s corpuscular philosophy as purely mechanistic was reinforced in Thomas Kuhn’s essay “Robert Boyle and Structural Chemistry”, in which Kuhn writes 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, as well as a cause of his rejection of explanations in terms of inherent characteristics of the ultimate corpuscles” (Kuhn 1952, p. 19). Kuhn, however, is not unique in attributing a strict Cartesian mechanism to Boyle. In fact, according to Joly (2008), this attribution can be traced 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 tells us 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].” (Joly 2008) Boyle does, in fact, make some very clear statements in favor of mechanism, especially his work The Excellency and Grounds of the Corpuscular or Mechanical Philosophy (1674). Indeed, the title of this work itself conflates the notion of corpuscularism with the notion of mechanism, as though these notions implied each other.

However, despite the received view among many historians of science, Robert Boyle’s own ontology cannot be easily categorized as purely mechanistic. A close examination of Boyle’s chemical writings, both published and unpublished, shows that “he was far from subordinating chemistry to mechanical philosophy, since he did not explain chemical phenomena by immediate and direct recourse to the mechanical affections of particles. As a matter of fact, he regarded chemistry as a discipline independent from mechanics. He explained chemical phenomena in terms of corpuscles endowed with chemical, rather than mechanical, properties. Accordingly, his chemical philosophy can be described as corpuscular, not as mechanical” (Clericuzio 1990, p. 563). “One of Boyle’s chief scientific pursuits was to explain chemical phenomena in corpuscular terms and to establish chemical foundations for corpuscular philosophy […] unlike [many of] his predecessors, Boyle’s combination of chemistry and corpuscular philosophy was based on an articulate theory of matter and was supported by a substantial amount of experimental evidence […] [Boyle’s theory of matter is commonly described as purely mechanical” (Clericuzio 2000, p. 103). However, “[a]lthough Boyle often repeated that the mechanical properties of corpuscles were to be regarded as the most general notions of natural philosophy, a closer analysis of his natural philosophy reveals a number of agents not operating according to the principles of mechanical philosophy. These agents are seminal principles, spirits, and ferments—which Boyle conceived as corpuscles endowed with the power of fashioning other parts of matter” (Clericuzio 2000, pp. 106–107).

From what has already been established, it is clear that Boyle was not unique in both embracing a corpuscularian theory of matter and rejecting strictly mechanical explanations of chemical qualities. As has been stated, corpuscularism does not entail 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). For example, when recounting his own experiments with the redintegration of saltpeter, Boyle interprets his results by appealing to the chemical properties of nitrogen, rather than by appealing to the strictly mechanical properties of shape, size, and motion of particles. When explaining the process of redintegration of potassium nitrate, in Certain Physiological Essays, “Boyle 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. In brief, for Boyle, chemical explanation retains its autonomy and cannot be reduced to a mechanical explanation that, without a doubt, sustains it but can never clarify it as such [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. Bref, pour Boyle, l’explication chimique garde son autonomie et ne peut être réduite à une explication mécanique qui sans doute la sous-tend mais ne peut jamais être explicitée en tant que telle] (Joly 2008, p. 4). Boyle, therefore, concurs with Paracelsian and other vitalists regarding the notion that chemical qualities and operations cannot be accounted for by reducing them to the mechanical properties of shape, size, and motion of particles. Although, he was critical of the Paracelsian doctrine of the theory of principles and qualities, “his criticism did not entail that all chemical properties were reducible to […] mechanical attributes [Boyle’s] aim was to reject the notion that sensible qualities were reducible to this or that ingredient of a mixed body. He [presented] the idea that a quality had relative character, namely, that it was generated from the constant interactions of different corpuscles, which themselves might not bear the quality in question [and] [h]e himself developed new and more sophisticated ways of detecting the chemical qualities of bodies” (Clericuzio 1990, p. 564). This suggests that Boyle saw chemical qualities as ‘emergent’ properties that could not be merely reduced to shape, size, and motion and “refrained from establishing a direct relationship between a given quality and a set of mechanical properties of the simplest corpuscles” (Clericuzio 2000, p. 108). Boyle is, in fact, openly critical of the Epicureans and Cartesians who “pretend to explicate every particular Phaenomenon by deducing it from the Mechanicall affections of Atomes or insensible particles.”2

The question, therefore, is this: How is Boyle able to reconcile his openly professed commitment to mechanical philosophy with his resistance to mechanical explanations of chemical qualities and operations? The answer lies in the particulate theory of matter that Boyle develops while conducting his early chemical studies. It is through this complex particulate theory that he is able to argue both for the mechanical philosophy and for non-mechanical explanations of chemical phenomena. In his manuscript “Of ye Atomicall Philosophy” (1651–1653), Boyle equates atoms with minima naturalia, particles that are not further divisible, although there is a definite distinction between Boyle’s conception and the Scholastic understanding of minima naturalia, in that “Boyle rules out the Aristotelian notion of form” (Clericuzio 2000, p. 116). He states, “by Atoms […] I understand not indivisible Mathematicall points […] but minima naturalia […] because tho they may be further divided by Imagination yet they cannot by Nature.”3 For Boyle, the primary properties of minima naturalia are understood as mechanical, that is, as shape, size, and motion.

However, in addition to adopting the notion of minima naturalia, Boyle also embraces a version of the notion of seminal powers to explain chemical qualities, although for him seminal powers are not spiritual but corpuscular in nature. 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 first-order and second-order. First-order corpuscles (minima naturalia) are described in terms of the mechanistic properties of shape, size, and motion. However, second-order corpuscles are compounded corpuscles that are endowed by God with seminal powers, that is, with specific “faculties or powers to fashion other parts of matter” (Clericuzio 1990, p. 583, footnote 107). Thus, although Boyle is not a vitalist and any inherent internal faculty of motion to first order corpuscles, he does posit second order corpuscles that have the special power of generation (Clericuzio 1990). There is an indication that, for Boyle, the corpuscular seminal powers are emergent properties of second-order corpuscles, that is, of compound corpuscles. In fact, “Boyle maintained that chemical qualities depended […] on the way in which the corpuscles that composed a given body were disposed to act, or to be acted on by, those of other bodies […] [and that they] emerged from the constant interactions of corpuscles passing from one body to the other […] he [thus] denied that they directly originated from the mechanical properties of their primary particles [first-order corpuscles]” (Clericuzio 1990, p. 588).

It is, therefore, clear from this discussion that Robert Boyle, who has been widely regarded as embracing a purely mechanistic corpuscular chemical philosophy, in fact holds a very complex ontology that is clearly neither vitalistic in the sense of Paracelsus, Basso, or even van Helmont nor entirely mechanistic in the manner of Cartesian mechanism. As a chemist, he is strongly committed to explaining chemical phenomena in ways that account for the qualitative changes that occur in chemical reactions and ‘transmutations’ and he is, therefore, not satisfied with reducing atoms and corpuscles to merely primary and entirely quantitative properties. Mechanistic explanations, for Boyle, just cannot satisfactorily account for chemical phenomena. However, although Boyle embraces the notions of vital spirits and ferments, he does not interpret these in Neoplatonic terms. Instead, he is instrumental in providing an analysis of vital spirits in chemical and physicalistic terms, while avoiding a strictly mechanistic account. Boyle’s theory about the general nature and classification of spirits was, in part, developed during his studies of the spirit of blood. In Memoirs for the History of Blood, Boyle “recorded that from the distillation of blood he had obtained, besides oily and phlegmatic parts, a clear liquor which, though probably it contained some phlegm, might be called spirit, because ‘it is fully satiated with saline and spirituous parts’ […] Boyle’s researches on the spirit of blood […] they brought about the abandonment of the belief that spirit as such—a homogeneous and vaguely defined [non-physical substance]—had to be regarded as the origin of vital spirit” (Clericuzio 1994, p. 64). As Clericuzio has argued, “a transformation of the notion of spirit by seventeenth century English chemical physiologists permitted them to view vitality as resulting from the chemical activity of substances rather than arising from a homogeneous spirit or soul.” It is precisely when vitality begins to be no longer viewed in theological or supernatural terms and to be viewed, instead, in naturalistic, albeit not mechanistic, terms that the stage is set for the advent of the Lavoisier’s Chemical Revolution.


As can be seen from the above, the shift from a vitalistic to a non-vitalistic theory of mater was not sudden and radical but, rather, followed a subtle, nuanced, and gradual path, from the sixteenth to the eighteenth century. Furthermore, the paradigm that ultimately supplanted vitalism in chemistry does not seem to have been mechanism but, rather, physicalism, that is, it was a shift from a dualistic ontology of matter and spirit to an ontology in which the only causally efficacious factors involved in natural phenomena were thought to be entirely physical and empirical factors. In this shift, the world soul itself was reduced from a spiritual to a physical ontological status and was, ultimately, identified with potassium nitrate or aerial niter. But, this physicalistic and naturalistic approach to the articulation of vital spirit and chemical qualities did not entail an entirely mechanistic approach. In fact, for chemical philosophy, physicalism and naturalism remained, in many regards, non-mechanistic.

Although, mechanical philosophy did advance eighteenth century chemistry to some extent and made important contributions such as, for example, the tables of affinity that were “based on displacement reactions and were supposed to show the relative strengths of the attractive forces between atoms” (Hankins 1985, p. 84), the mechanical philosophy never quite succeeded in explaining “chemical properties such as acidity, alkalinity, metallicity, salinity, and the chemical operations of combustion, fermentation, and distillation [Although] Newton [for example] had hoped to reduce chemistry to a science describing the mechanical interactions between atoms […] that hope was not fulfilled […] The Chemical Revolution came about not by any triumph of the mechanical philosophy but by a rationalization of these traditional chemical qualities and operations” (Hankins 1985, p. 84). I would argue that this rationalization most definitely occurred with the demise of vitalism. However, this demise did not so much result in the victory of mechanism but, rather, in the victory of physicalistic and naturalistic articulation of chemical qualities. “[I]f the revolution chemistry was not mechanical, it was definitely physical […] and resulted from [Lavoisier to his associates] bringing the physical theory of gaseous states into chemistry […] Lavoisier’s elements were those simple substances that could be analyzed no further […] they were known by chemical […] characteristics” (Hankins 1985, p. 112). With this dissolution of the traditional theory of the elements and with a physicalistic, albeit not mechanistic, understanding of chemical properties and operations, eighteenth century chemistry ultimately shed its vitalistic cloak. But this development was less the outcome of the dominance of mechanism than it was the result of a two-century long process, involving alchemists, chemists, and chemical philosophers, that slowly transformed and naturalized minima naturalia, semina rerum, and vital spirits. Put briefly, when the world soul became potassium nitrate, the ‘disenchantment of the world’ had begun.


Cited in Clericuzio (1994, p. 52).


Cited in Clericuzio (2000, p. 138).


Cited in Clericuzio (2000, p. 117).


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