"Mechanical and Iatrochemical Theories in 17th-Century Physiology"
University of Sydney
Sydney, Australia, 20 February, 2009
In this subtle and well-argued paper, which takes up and develops some of the aspects of his 2000 book, Elements, Principles, and Corpuscles, Antonio Clericuzio seeks to challenge the traditional scholarly distinction between iatromechanism, representedmost prominently by Descartes, and iatrochemistry of the sort practiced by Paracelsus and J.-B. van Helmont. Between the book and the numerous articles and papers that have followed, on the one hand, and on the other hand the equally forceful revisionist work of scholars such as John Henry, it seems to me however that it may be time now for scholars who do not draw a firm boundary between quantitative corpuscalarianism and qualitative chemical philosophy, but instead recognize an enormous middle ground of qualitative corpuscularianism, to stop thinking of themselves as the eternal opposition and to pronounce their historically more rigorous and adequate interpretation of the lay of the land in the 17th century instead as ‘the new tradition’.
If we could make the two traditions distinct, if we could separate them conceptually even as we acknowledge that nowhere can they be found in their pure forms, we might say that, for an iatromechanist, living beings are ontologically of a pair with nonliving things, since their operations are peformed by particles of inert matter following the owhat Descartes calls the "minor laws" that govern the rest of nature. Of iatrochemistry, we would say in contrast that the body is, as Clericuzio puts it, a chemical ‘laboratory’, whose most basic processes are chemical, and ultmatiely qualitative, changes.
Clericuzio surveys important moments of the chemical tradition from early Paracelsianism through Robert Boyle, (who is the terminus ad quem of Clericuzio’s story) showing how, particularly in the context of English physiological work of the second half of the 17th century, where Descartes had only very limited impact, the line between the two traditions is not nearly so distinct as we have ordinarily believed.
In the early Paracelsian tradition, archaei, spirits, ferments, and seeds play a crulcial part for the understanding of 'living anatomy'. 'Living anatomy' discloses the incorporeal principles ruling the organs, and that ultimately distinguish the living body from a cadaver. In this tradtion, chemistry is the way to discover the hidden properties of bodies, the features of a living being that it has qua living thing rather than qua bodily thing.
By the time of Boyle, the one feature of early Paracelisan living anatomy that would endure in good health, and that indeed would be invoked for the explanation of all manner of bodily phenomena, was fermentation. As Boyle writes in the Free Enquiry Into Received Notion of Nature: "I look not on a human body, as on a watch or a hand-mill, i.e., as a machine made up only of solid, or at least consistent parts; but as an hydraulical, or rather hydraulico-pneumatical engine, that consists not only of solid and stable parts, but of fluids, and those in organical motion: and not only so, but I consider that these fluids, the liquors and spirits, are in a living man so constituted, that in certain circumstances the liquors are disposed to be put into a fermentation or commotion. Works, 12, p. 473. italics are Boyle's. Hormetic (from the Greek όρμητικός) means having the property ofexciting (OED).
I found this passage particularly interesting for my own work, as in a manuscript of Leibniz’s that I’ve recently edited we find Leibniz claiming: “Animal ergo esse machinam non tantum Hydraulico-Pneumaticam, sed et quodammodo Pyrotechnicam merito dicemus.” Earlier, I had thought that Leibniz was saying something new, but now this seems to me a paraphrase: You’ve got the lowest level, what the being does share with a watch; then what the activity of the spirits add; then you’ve got the capacity for fermentation, which manifests itself in, as Leibniz says, ‘innumerable small explosions’.
In this connection, I would be interested to know: What is Boyle’s understanding of animal economy? Leibniz had presumed that it just was the elaboration of the principles of the hydraulico-pneumatico-pyrotechnical machine, but Clericuzio seems to see this term as having a different acceptation in Boyle.
It seems to me that if the traditional dichotomy opposed by Clericuzio is to apply to anyone, it is to Harvey, who adamantly rejects many elements of the chemical legacy. He dismisses spirits as a deus ex machina and a subterfuge, and he attacks the Paracelsians, in particular Severinus, who claims that “bodies are produced from spirits and in turn resolved into spirits.”
Harvey also believes that respiration serves to cool the blood, and with this we see the first instance of what I believe is actually a sub-theme of Clericuzio’s work, one that is not explicitly stated in the initial framing of the revisionist thesis concerning the dichotomy between iatromechanism and iatrochemistry. This sub-theme has to do with the debate between early modern authors as to the role of the air, or more generally, the external world, in the maintenance of the body. For Harvey, respiration serves to cool the blood, a thesis later argued against by Locke in his little known early work Usus respirationis. Richard Bathurst, about whom I’ve learned a great deal from Clericuzio’s work, argues that aerial nitre is the vital principle in air that is mixed with the blood in respiration. Boyle for his part was stimulated by Locke to write his natural history of blood. (Was this, I found myself wondering, before or after Locke’s own Usus respirationis?)
Metaphysically speaking, it seems to me that there is a very interesting story to be told about the early modern engagement with the fact that an animal body, unlike a rock or pile, endures in existence only through constant interchange with its environment, that is to say, respiration and nutrition. In a corporeal-substance metaphysics, then, the living body is distinguished by the fact that it has not the greatest but the least degree of physical cohesion, but at the same time is able to maintain its form through the fountain-like flux of matter. The study of the role of air in maintaining the flow of fresh blood; along with the study of the transformation of food into chyle, seems to me to be one of the most important elements of the experimental background to the metaphysical modelling of corporeal substance by philosophers, some of whom do not acknowledge the sources of their interest in living anatomy.
Of course, the big question in any discussion of the role of spirit in physiological processes is: what do you mean by spirit? Descartes is often lauded for being the first to physicalize spirit, yet van Helmont conceives spirit as an alkaline volatile salt. The proper question, it seems, is not whether it is physical or not, but rather whether it is chemical or not: if it is, then it will have irreducible qualitative properties, even though it can be analyzed to some degree in terms of its composition.
Glisson explains rickets in terms of spirits rather than in terms of humours, as the Galenists had done. In the Anatomia hepatis of 1654 Glisson adopts unambiguously chemical explanations. While Harvey maintains that blood itself is the active principle, Glisson says that it is the admixture of spirits into blood that makes it active. Following Glisson, Walter Charleton sees blood as originating by the action of the vital spirit. In contrast with Glisson, Charleton combined chemistry with the corpuscular theory of matter. In this broad, sweeping suvey, what quickly becomes clear is the lack of any real opposition between the chemical and the mechanical. Willis sums up this harmony nicely. For him, the mechanical philosophy valiantly "undertakes [to explain]mechanically the unfolding of things, and accommodates nature with working tools, as it were in the hand of an Artificer, and without running to occult qualities, sympathy, and other refuges of ignorance.” Yet Willis nonetheless prefers the chemical philosophy. Why? Because it is more adequate to the phenomena. Mechanism might work just fine in accounting for planetary orbit or the motion of billiard balls, but for the gross, macro-phenomena of living bodies qualitatively irreducible processes must be invoked. In this respect, it is medicine or biology that announces the need for chemistry in early modern science, and it is this need that undermines the pure mechanist program.
Yet we must take Descartes’s word for it when he annonced his intention to explain phenomena such as fermentation in non-chemical terms. In the view of a scholar such as Betty Jo Dobbs, Descartes’s incorporation of the concept of fermentation into his physiology amounts to a prime example of the habit of early mechanists to restate common cultural assumptions “in terms of corpuscularian mechanisms that disguised but by no means eliminated their vitalistic components.” Yet this criticism may not be entirely fair. While there is no doubt some truth in the general point that the mechanists gained nothing in explanatory force by substituting ‘microstructure’ for ‘form’ or ‘virtue’, it is clear that Descartes conceives fermentation as a straightforwardly thermomechanical process, and that he conceives the changes it brings about not in terms of the emergence of new forms, but in terms of the quantitative alteration of preexisting corpuscles. If he could not account for the details of these changes at the microlevel, this does not mean that in granting to fermentation a central place in physiological phenomena, he does not have reason to hope that someday it might be explained in entirely mechanical terms.
But Clericuzio’s more nuanced, non-dichotomous approach does not stand alone, and for this reason it is hard to see why a Dobbsian approach should be treated, today, as hegemonic. As Wilson notes, historians of early modern science who reject the cruder view prevalent among historians of philosophy, according to which early 17th-century mechanism initiated a swift ‘paradigm shift’, have also been moving away from the view that early modern thinkers first embraced a thoroughgoing mechanist world-view only to make some concessions and allowances later in the century whereby a certain amount of qualitative description of nature and ontological commitment beyond bodies with their mass, figure, and motion were allowed to creep back in. In place of this account, a new picture has emerged on which a strict or pure mechanism never came to predominate in the first place, so that when figures such as Newton incorporated forces and entities in the latter half of the 17th century that would have been offensive to Hobbes and Descartes, this was not due to any back-tracking or revisionism, but only because the landscape of scientific ontology had not really been painted monochrome by Newton’s predecessors at all. As John Henry describes the century (at first facetiously, and then in earnest):
As every historian of science ‘knows,’ the essentially unworkable mechanical philosophy was transformed by the genius of Newton who re-introduced ‘occult qualities’ into natural philosophy…. The historiographical emphasis on the radical revisionism or innovatory nature of Newton’s account of occult active principles and the concentration on non-mechanist sources of influence like alchemy tends to perpetuate the view that English mechanical philosophy before Newton followed the essentially unworkable Cartesian programme in which matter was completely inert and could only act by virtue of its ‘force of motion’ in collision with other parts of matter.
In sum, there is no longer any reason to be haunted by anachronistic dichotomies between the triumphant right theories of the past on the one hand, and the doomed obscurantist ones, on the other, of which the corpuscularian-chemical dichotomy was likely the most difficult of all to eradicate.
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