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A Mutual Divide: Experiment vs. (Cartesian) Speculation in Mid-Seventeenth Century Dutch Medicine

This is a guest post by Evan Ragland.

In 1639, the Dutch anatomist and physician Franciscus Dele Boë Sylvius (1614-1672) thrust experimental physiology before the public eye when he demonstrated the Harveian circulation of the blood in the Leiden public gardens. These anatomical investigations unfolded within and partially constituted the growing controversy over the motion of the heart and blood. At some key moments, this controversy resembled the structure and rhetoric of the experimental-speculative distinction.

For the anatomists, Harvey’s description of a muscular heart contracting at systole to expel blood into the arteries was observationally and experimentally proven.  In contrast, many leading anatomists found Descartes’ anatomy to be fallacious and outmoded. Sylvius’ demonstrations convinced one critic, Johannes Walaeus (Jan de Wale, 1604-1649), who became an ardent supporter of the circulation. In 1645, Walaeus attacked the Cartesian explanation of the heart’s motion:

    Certain men with brilliant minds [ingenium praeclarum] judge that the blood is thrust out because it is immeasurably rarefied by the heat of the heart, and so demands a bigger place, and then dilates and lifts up the heart. […] [Yet] in truth the blood does not leap out from the heart on account of the rarefaction, as we have often seen in strong dogs with the tip of their hearts cut off. Because of the outflow of the blood, the heart is not half filled, but still erect: thus, it is not filled by rarefaction. In the subsequent constriction the portion of the blood in the heart was ejected more than four feet, so that we and our neighbors in the large crowd were befouled. From which it is evident that the blood is propelled by the part.

Strikingly, at least one of Descartes’ close friends and supporters, Cornelis van Hogelande (1590-1676), embraced the distinction between experimental and speculative approaches the anatomists propounded, but favored the speculative method.

“The Neoterics,” following after Harvey, added superfluous experimentation to already conclusive reasoning. They proceeded, “not only according to the manifest laws of mechanics […] but, instead, not having enough trust in the grace of reasoning [ratiocinatio], they turned themselves to girding and supplementing these laws with scrutinizing investigations or real and sensual disquisitions, and to dissecting living animals of every kind.”

For his own positive account, Van Hogelande relied on reasoning from mechanical principles. He could, though, throw a bone to the experimentalists:

    As a favor to those who are distrustful of ratiocination and believe experience alone, I will not be amiss in adding on the following easy experiment, in confirmation of the truth of the aforesaid [conclusion]. [Experiment dissecting an eel’s heart, and then adding blood when the motion has ceased, causing increasing motion.] [A]nd I even repeated this experiment in its particularities with similar success, while the printer hurried. Which I add lest anyone assume that I collected those preceding reasons a posteriori (that is, with the experiment having first been done).

This division lasted. In his later medical disputations from the late 1650s and early 1660s, Sylvius set out to resolve the dispute between Harvey and Descartes, “the two most brilliant Lights of this age.” Harvey taught “according to the custom of the Physicians, as well as the Sensible Philosophers, and according to the testimony of the external Senses.” Descartes, on the other hand, “trusting more in the laws of his own Mechanics, rather than in his external Senses, suspected and believed that the Ventricles of the Heart and the Arteries were Dilated and Contracted simultaneously.” Once again, the distinction between experimental anatomy and Cartesian speculation is crisp:

    For whatever even the most subtle and sagacious Genius [Ingenium] is able to think up that is most probable and plausible to the human Mind, every such thought, if it looks to the Medical Art, ought to be suspected as False by the Prudent, until Experience the Teacher of Truth has manifested that it is True, that is, that it has actually been observed in the things themselves as it has been imagined [fingitur].
    God forbid that among the legitimate Sons of Physicians anyone should be discovered who is so lazy, that they […] would rather delight in adhering to his own figments and Chimeras, and to those of others.

Shortly after, Sylvius freely admitted that Descartes was a “famous Mathematician and industrious Philosopher.” Drawing the lines of discipline and identity so that Descartes remained a successful mathematician and philosopher was the gentlest criticism, but one that barricaded him from a place among “the legitimate Sons of Physicians.”

There are, however, complications for this neat typology. Several Dutch anatomists at the time evinced some support for Cartesian philosophy, and later professors of medicine were staunchly Cartesian. And Sylvius repeatedly announced his support for something very like Cartesian mechanism as the preferred and future form of explanation and ontology, even in medicine. Yet a mutual division similar to the ESD remained at the heart of these early anatomical controversies.

4 thoughts on “A Mutual Divide: Experiment vs. (Cartesian) Speculation in Mid-Seventeenth Century Dutch Medicine

  1. Your article raises an important question with respect to the ESD: What is the relation of a distinction between experimental and speculative philosophy to very similar distinctions in other fields of study? Medicine, mathematics or even art theory (e.g. in Karel van Mander’s distinction between painting “from the mind” and “according to life”) had reasonable well defined categories to distinguish between purely theoretical work and practical exercises long before the experimental/speculative divide became common in philosophy. Sometimes theoretical and practical parts of the field were directly linked, e.g. using the dialectic of Petrus Ramus, but there are also cases, where both parts were regarded as antagonistic and mutually exclusive. The debate about Cartesian medicine is one such example. So, is the emergence of the experimental/speculative divide in philosophy essentially an import from other scholarly fields?

  2. Hi Gerhard, I have two thoughts on this.

    1. It is true that, in some cases, early modern philosophers employed an experimental-speculative distinction between different disciplines or between theoretical and practical or empirical parts of the same discipline. However, what is distinctive of self-declared early modern experimental philosophers (e.g. Locke, Newton, Diderot, and Reid) is that they understood the experimental-speculative distinction as a distinction between alternative, incompatible methods. It is in the light of this methodological experimental-speculative distinction between alternative approaches to natural and moral philosophy that we should interpret early modern experimental philosophers (more here). It is probably true that the methodological distinction derives from transformations of earlier disciplinary distinctions. However, I take the methodological distinction to be still remarkably different from the disciplinary distinctions, including earlier distinctions between speculative (or theoretical) and experimental (or empirical or practical) parts of disciplines which were not usually included within philosophy.

    2. The texts that Evan cites are from the 1640s onwards, which is roughly the time in which the (methodological) experimental-speculative distinction was being introduced within philosophy in England. I take this to mean that this distinction, or at least the presuppositions for introducing it, were “in the air”. Natural philosophy and medicine are related areas, so it should not be surprising that a methodological experimental-speculative distinction could be developed as easily within medicine as within natural philosophy. In fact, English authors like Sydenham would soon export the experimental-speculative distinction from natural philosophy to medicine.

    Does this sound persuasive? In particular, would you agree with my suggestion that a methodological experimental-speculative distinction was “in the air” in the 1640s? Or am I underestimating the degree to which distinctions between competing experimental and speculative methods were present outside of philosophy before the mid-seventeenth century?

  3. Hi Alberto,
    I agree with much of what you’re saying here, but I think the ‘in the air’ part needs to be rendered more precisely. Since the second half of the 16th century, there is a substantial debate about the relation between a purely theoretical, speculative analysis and a study guided by empirical methods. This debate pertains to many different fields of knowledge, with medicine and mathematics probably the most prominent ones. One can interpret Ramus’ dialectic of theory and practice as a methodological reflection of those debates (at least this is how some early 17th century philosophers have interpreted it). In these terms the ESP distinction was a latecomer to this debate, at least partly because empirical (natural) philosophy was considerably younger than empirical studies in other disciplines. In a sense, once scholars accepted academic studies with a methodological foundation in observation, the relation between ‘theory’ and ‘practice’ needed to be determined, was in the air, so to speak.
    Your point of the ESP distinction as stating incompatible alternatives and not different, but complementary modes of inquiry is important here. Certainly, most mathematicians around 1600 would have considered practical mathematics and mathematical theory as complementary, but does that also pertain to medicine? My expertise on that field is limited, but I wouldn’t be surprised, if we wouldn’t find positions that reject purely speculative approaches in medicine some time before the critique of Cartesian medicine in Holland around 1640. So, the question remains whether in the ESP distinction philosophy imports a medical debate (or maybe even a chemical one) or redefines a methodological problem that had existed in other disciplines, but only pertained to philosophy from the mid-17th century onwards.
    Another consequence of your point is that, of course, understanding the ESP distinction as incompatible alternatives, as proposed by Boyle or Newton, was not the only possible (and actual) interpretation in 17th century philosophy (e.g. Leibniz and subsequently Wolff).

  4. Hi Gerhard,

    Thanks for your comment and sorry for the late reply. Good point: it is important to see the rise of the ESD in the context of the debates between theory and practice.

    The problematic status of natural magic and mechanics is probably relevant to these debates. They were theoretical disciplines, but they were not merely speculative. They involved a practical, operative dimension. Bacon classed them as parts of operative, not merely speculative natural philosophy, and this appears to be an ancestor of experimental natural philosophy as opposed to speculative philosophy.

    It would be very interesting to find anti-speculative approaches in medicine before the 1640s. Vesalius’ emphasis on the importance of practising anatomical dissections in order to gain knowledge of the human body can probably be read as a critique of purely theoretical or speculative approaches.

    A field in which we have found very explicit anti-speculative polemics before the 1640s is religious literature. Peter Harrison has shown that a speculative-experimental distinction was present in the English religious literature in the first half of the eighteenth century, with most writers promoted experimental religious against speculative religion.