“Last year [Henricus Regius] published a book entitled Fundamenta physicæ [sic] in which, concerning physics and medicine, it seems he has taken everything from my writings, those I have published as well as a still imperfect work on the nature of animals that fell into his hands; nevertheless, because he transcribed it poorly and changed the order, and denied certain truths of metaphysics on which all physics must be founded, I am obliged to disown the work entirely.” (Descartes, Preface to the French translation of Principia Philosophiæ, 1647)
René Descartes (1596–1650) is well known to the general public as “the father of modern philosophy,” the creator of that paradigmatically modern movement, Cartesianism. By contrast Henricus Regius (Henrik de Roy; 1598–1679) is known for the most part only to dedicated specialists. Yet a consideration of the case of Regius can serve to illustrate the extent to which Descartes did not have complete control over his creation.
This case is a curious one. Regius was a professor of medicine at the University of Utrecht. He was much taken with the views he had read in the scientific essays accompanying Descartes’s Discours de la méthode (1637), and was one of the first to introduce Descartes’s new mechanistic account of the material world into the Dutch academy. Regius also was the point man for the defense of Descartes against the attacks of his traditionalist critic, the Utrecht Rector Gibertus Voetius. Descartes subsequently wrote concerning Regius that he is “so confident of his intelligence” that there is nothing in his writings that “I could not freely acknowledge as my own” (Epistola ad Voetium, 1643). Yet a mere four years later, in the passage from his preface cited above, Descartes angrily denounces Regius, charging him with plagiarism, and incompetent plagiarism at that. So how is it that in such a short period of time we go from Regius the trusted Cartesian disciple to Regius the despised Cartesian outcast?
The main clue to the answer lies not in Descartes’s charge of plagiarism (which Regius vigorously denied), but rather in his claim that Regius went astray in denying “certain truths of metaphysics on which all physics must be founded.” The reference here is to the fact that in a draft of his Fundamenta physices—the work that prompted Descartes’s denunciation—Regius disputes both Descartes’s arguments for the existence of God and his claim that reason alone can reveal that mind and body are distinct substances. When in a 1645 letter Descartes reacted with “astonishment and grief” to this disavowal of his metaphysical views, Regius attempted to placate his former promoter by excising the offending elements from the published version of his Fundamenta (1646). However, matters had gone too far for such gestures to have any effect. Even in the sanitized version of Regius’s text, Descartes could see only a dangerous repudiation of his view that physics must be founded on secure metaphysical foundations.
Subsequent to Descartes’s denunciation of Regius in his 1647 preface, the rift between the two only widened. That same year one of Regius’s medical students circulated a pamphlet that outlined Regius’s differences with Descartes, including the ones excluded from the Fundamenta. Descartes immediately responded by insisting again on the soundness of the metaphysical foundations for his physics. Soon after Descartes’s death his literary executor, Claude Clerselier, criticized Regius in print for his ingratitude toward Descartes and exhorted him to return to the Cartesian fold by embracing Descartes’s conclusions regarding God and the human soul.
On the narrative we find in Clerselier, Regius was a rebel against the Cartesian cause. But it is important to recognize another side to the story. For instance, there is a reference from the Rotterdam physician James de Back to “the most learned H. Regius, Professor of Physick in the University of Utrecht, and a notable follower of de Cartes” (“Discourse on the Heart,” 1653). Though he undoubtedly was aware of Descartes’s public repudiation of his fellow Dutchman Regius, De Back was concerned here with Descartes’s controversial view that the motion of the heart consists in the diastole, a view that Regius developed in an original way. In this medical context such physiological issues would be more to the point in determining an ideological connection to Cartesianism than the sort of metaphysical issues that separated Descartes from Regius. With respect to the former, Regius did indeed adhere—and was recognized as adhering—to a distinctively Cartesian line. In fact, Regius was at the center of a network of Dutch Cartesian physicians and medical professors who owed their training in mechanistic physiology either directly or indirectly to him.
At this point one might well protest that the question of whether or not one should apply the label ‘Cartesian’ to Regius is merely a verbal one. However, I think there is a substantive issue here concerning our understanding of Descartes’s influence on modern thought. One can view him as bequeathing a complete and seamless system, acceptance of which is essential for someone to be considered a follower. But another perspective is provided by David Hull’s clever and instructive attempt to understand the nature of the conceptual system “Darwinism” in terms of a Darwinian analysis of biological species. According to this analysis, there is no expectation that there will be a set of phenotypic traits that all and only members of a particular biological species possess throughout time. A species is rather a population likely to be marked by considerable phenotypic plasticity. What unites the diverse members of a species is a particular historical origin and line of descent. It is similarly the case, Hull claims, with respect to Darwinism as a conceptual entity (“Darwinism as Historical Entity: A Historiographical Proposal,” 1985). What I am suggesting here, in a preliminary way, is that the curious case of Regius indicates that we also should view Cartesianism as akin to an evolving historical species, one diverse enough to include the views of a person Descartes himself disowned.
Featured image: The disbanding of the ‘waardgelders’ (mercenaries in the pay of the town government) by Prince Maurits in Utrecht, 31 July 1618, by Joost Cornelisz Droochsloot. Public domain via Wikimedia Commons.