Physics and Metaphysics in Descartes and in his Reception

Delphine Antoine-Mahut, Sophie Roux, Delphine Antoine-Mahut, Sophie Roux

• Publisher: Routledge
• Year: 2018
• ISBN:
  9780429787553
• Edition: 1
• Topic: Philosophy
• Subtopic: Philosophy History & Theory

This volume explores the relationship between physics and metaphysics in Descartes' philosophy. According to the standard account, Descartes modified the objects of metaphysics and physics and inverted the order in which these two disciplines were traditionally studied. This book challenges the standard account in which Descartes prioritizes metaphysics over physics. It does so by taking into consideration the historical reception of Descartes and the ways in which Descartes himself reacted to these receptions in his own lifetime. The book stresses the diversity of these receptions by taking into account not only Cartesianisms but also anti-Cartesianisms, and by showing how they retroactively highlighted different aspects of Descartes' works and theoretical choices. The historical aspect of the volume is unique in that it not only analyzes different constructions of Descartes that emerged in the 18th, 19th and 20th centuries, but also reflects on how his work was first read by philosophers across Europe. Taken together, the essays in this volume offer a fresh and up-to-date contribution to this important debate in early modern philosophy.

Part I

Historiography

1 First Philosophy, Metaphysics, and Physics

The Implications of Order in Cartesian Philosophy and in the Philosophy of Enlightenment

Mariafranca Spallanzani

I

I would think I knew nothing in physics if I could say how things can be but could not demonstrate that they can not be otherwise. Such demonstrations are perfectly possible once physics has been reduced to the laws of mathematics. I think I can provide them for the small area to which my knowledge extends; but I did not do them in my Essays because I did not want to present my principles there.¹

These few lines from the letter to Mersenne dated 11 March 1640, three years after the Discours, contain one of the clearest statements Descartes provides concerning his theory of truth in physics. Both as an instance of the epistemological foundations of a science yet to be constructed and as a recognition of the limits of the already existing sciences, these lines might well summarize Descartes’ intellectual path from the Discours and the Essais to the Meditationes, that is, from natural science to first philosophy.

As a philosophical reflection on the modalities of judgment, Descartes in this letter engages in the debate at that time concerning the models of scientific knowledge and delineates the elements of his rationalist epistemology of the science of bodies through a strict correlation between physics and mathematics. As a philosopher, Descartes affirms that only a necessary physics can resist and respond to the objections put forward by skeptics, and that only a true physics can emerge victorious from both the ruins of the Aristotelian doctrine of forms and from the ambiguities of modern scientific hypotheses. The legitimization of physics must satisfy above all the demand for the justification of the laws of nature, that is, for the mathematical truths created for nature and the demand for stability for physical objects, i.e., bodies as objects of science.

These are difficult but fundamental questions for Cartesian science in its claim of necessity, truth, and reality. Can the objects of physics be known through the clear, distinct, and complete idea of extension?² Moreover, can bodies be truly subject to a mathematical treatment that guarantees their necessity, and can they be comprehended through the chain of theorems that follow from their definition? Lastly, are bodies true beings, in which the evidence of reason grasps the truth of the thing, in line with the necessary conditions of a real physics? Or are they no more than a seductive construction of the imagination, an extraordinary production of the intellect?³

Descartes’ interests as a man of science are intertwined with his demands as a philosopher. According to his philosophy, the path that leads to the truth and necessity of science is not provided by or within science itself, but goes beyond science, without, however, sidestepping the imperative of order: it is defined as the way to the founding principles. The theoretical solution that allows physics to be saved from the dangers of arbitrariness and the risks of contingency, as well as from any purely hypothetical solutions, can be no other than a doctrine of the principles. This doctrine will be given the old Aristotelian name of “first philosophy” but it will be completely renewed, in an anti-Aristotelian perspective. First philosophy, which concerns “in general all the first things”⁴ conceived by the soul, is defined by Descartes as the science of the first principles that underpin all other knowledge, which naturally derives from these principles according to the order of a coherent chain—or coherent chains—of deductions. The movement of deduction is guided by the sole criterion of evidence in a multiplicity of points of access to the truth. The reversibility of the deductive connections guarantees the consistency of the solutions by means of the distinction between the proofs given “by the effects” and the explanations given “by the causes” mentioned by Descartes in his response to Morin on 13 July 1638.

Descartes repeatedly expressed his doubts regarding the possibility of concretely achieving physics by means of the principles. “I still cannot see anything to persuade me to present them in the future,” he confessed to Mersenne again in March 1640. Nevertheless, his solution had already been clearly outlined in the 1630s, while he was fully focused on “the great mechanics of nature.” His solution was “to demonstrate the principles of physics by means of metaphysics.” It will be legitimated in the Meditationes de Prima Philosophia thanks to the discovery of the immaterial first principles, i.e., the existence of the soul and of God, which, according to him, give physics the theoretical consistency of necessity, truth, and reality. The existence of the Ego sum, with the demonstration of the unconditional validity of the general rule of truth, along with the existence of infinite and perfect God, creator of the existences and the essences—the “foundations of metaphysics” mentioned in the Discours—act indeed as the “first principles” of physics, offering it the intelligibility, stability, and truth that allow physics to be possible, necessary, true, and real. Physics is possible in its geometric model—“my physics is no other than geometry”—from which can be inferred its necessity, comparable to the necessity of geometry; physics is true in its object, i.e., the extension, which the intellect conceives as “a determinate nature … that is eternal and unchanging”⁵ and essentially distinct from the soul.

Descartes intended to complete his project of a “scientia perfectissima” of nature that proceeds from causes to effects⁶ in the Principia Philosophiæ, in which a strong theory of the principles, anchored to metaphysics and presented as the condition for the passage from a mathematics of possible beings to a physics of necessary and real beings, sustains the equivalence between the object of geometry and the matter of bodies. In this work, written in 1644, the entire realm of physics, articulated according to the a priori principles of metaphysics, takes the shape of a true rational system of the world that is true and real: true of the truth of the clear and distinct idea of bodies, i.e., the extension,⁷ and real of the reality of the mathematical laws created by God for the matter in the eternity of his immutable decrees.

Equivalent in the Principia to first philosophy, metaphysics thus makes Descartes’ physics a philosophical physics,⁸ and even a metaphysical physics.⁹ Metaphysics is a reasoned knowledge of the laws of nature founded on the clear and distinct, true, and real principles that it imposes on physics as the first principles of reason that also act as causes, according to the equivalence established by Descartes causa sive ratio.¹⁰ Writing the Principia “as a Philosopher”¹¹ and providing all “the true reasons,”¹² Descartes offers a unified corpus of his philosophy¹³ that is tied to the Meditationes as regards the metaphysical subjects of the first part—“almost the same things,” he confirms—but that is put forward in “another style” and “in such an order” that it could “easily be taught.”¹⁴

“As a Philosopher,” Descartes renews in the Lettre-Préface to his work the traditional figure of the tree of philosophy:¹⁵ the trunk—physics—grows on the roots of metaphysics “as upon rocks” and extends into the three branches of medicine, mechanics, and morals according to the law of the unity of universal wisdom,¹⁶ which in the end Descartes offers to men as the most noble and precious fruit of the philosophical orchard.

However, the letter-response to Mersenne written by Descartes on March 1640, which defines the philosophical conditions of the truth of physics, also contains one of the most explicit admissions of the limits of his Essais published with the Discours: this work, according to Descartes, risked missing the truth of science because of the voluntary omission of the principles. The readers of the Discours had repeatedly noted these limits, lamenting the obscurities, the omissions, sometimes even the “ambiguities”¹⁷ of a work that presented important scientific results that, however, were never entirely developed, and the “key”¹⁸ to them apparently deliberately kept hidden. The readers agreed that these results were excellent but they were put forward more as oblique suppositions than through complete “explanations” and exhaustive “clarifications.” In their opinion, the obscurities, omissions, and ambiguities made the work unsatisfactory and Descartes’ physics weak: it was not a system of the world, but an orderly exploration of natural phenomena.

Descartes himself, for that matter, had openly recognized the limits of his work. The principles of the Essais were insufficient and their demonstrations incomplete due to the elisions produced by the model of a hypothetical-deductive science. Furthermore, the fourth part of the Discours was obscure because of the simplification of its arguments due to the treatment of metaphysics as an essay of method and to Descartes’ philosophical reticence in this text written in French for an audience of readers who were not necessarily philosophers.

Only the Latin text of the Meditationes de Prima Philosophia, dedicated to the Doctors of the Sorbonne, would in fact render all theoretical and argumentative complexity of Descartes’ metaphysics. In this work, Descartes conceives first philosophy as the universal science, and metaphysics a specific science¹⁹ not far removed from theology.²⁰ Radically overthrowing all traditional paradigms, Descartes’ theory of truth abandons the classical theory of categorical adequacy, in the same way as it rejects scholastic metaphysics in both its general ontological function and its specific articulation in theology, pneumatology, and cosmology. Indeed, first philosophy is defined as the science of “the first principles of knowledge,” which the universality of the Mathesis validates not according to a hierarchy of the genera of being but according to the order of the reasons. Following Aristotle but going against his model, Descartes continues to think of metaphysics in relation to first philosophy: “the most evident and certain” principles of first philosophy—the finite soul and God, “ens summe perfectum et infinitum”—are “intellectual natures,”²¹ and thus metaphysical subjects.

This theory was not entirely new in Descartes’ philosophy: the two subjects of metaphysics had appeared as titles in the “petit Traité” written in 1629—“the e...

Table of contents

• Cover
• Title
• Copyright
• Contents
• Abbreviations
• Introduction
• Part I Historiography
• Part II Physics and Metaphysics in Descartes’ Time
• Part III European Receptions
• Bibliography
• Contributors
• Index Rerum and Nominum