This paper draws attention to the crucial importance of a new kind of precisely defined law of nature in the Scientific Revolution. All explanations in the mechanical philosophy depend upon the interactions of moving material particles; the laws of nature stipulate precisely how these interact; therefore, such explanations rely on the laws of nature. While this is obvious, the radically innovatory nature of these laws is not fully acknowledged in the historical literature. Indeed, a number of scholars have tried to (...) locate the origins of such laws in the medieval period. In the first part of this paper these claims are critically examined, and found at best to reveal important aspects of the background to the later idea, which could be drawn upon for legitimating purposes by the mechanical philosophers. The second part of the paper argues that the modern concept of laws of nature originates in René Descartes's work. It is shown that Descartes took his concept of laws of nature from the mathematical tradition, but recognized that he could not export it to the domain of physico-mathematics, to play a causal role, unless he could show that these laws were underwritten by God. It is argued that this is why, at an early stage of his philosophical development, Descartes had to turn to metaphysics. (shrink)

In this paper, I examine the manner in which Descartes defends his Vortex Hypothesis in Part III of the Principles of Philosophy, and expand on Ernan McMullin’s characterization of the methodology that Descartes uses to support his planetary system. McMullin illuminates the connection between the deductive method of Part III and the method Descartes uses in earlier portions of the Principles, and he brings needed light to the role that imaginative constructions play in Descartes’s explanations of the phenomena. I develop (...) McMullin’s reading by bringing further attention to the constraints that Descartes places on the imagination in Part III. I focus in particular on the way in which Descartes uses metaphysical truths concerning God’s nature to support his general description of the planetary system, and on the way he relies on a mathematical standard of intelligibility to defend his proposals about the configuration of matter. Attending to the role of metaphysics and mathematics in Part III shows that Descartes’s arguments for the explanatory power of the Vortex Hypothesis are more effective than McMullin suggests. The reading I forward also offers important perspective on how Descartes’s hypotheses in Part III can be seen as both metaphysically and mathematically well-grounded. (shrink)

It is common to assume that Descartes did not have a conception of an object's matter density independently of its size, but this is a rather incomplete assessment of the early modern natural philosopher's theory. Key to our understanding of Descartes's physics is a consideration of the ratios between the quantities of the different types of matter in which an object consists. As these ratios determine the degree of an object's porosity and elasticity, they also affect in Descartes's theory the (...) phenomena of gravity and weight. (shrink)

Newton began his Principia with three Axiomata sive Leges Motus. We offer an interpretation of Newton’s dual label and investigate two tensions inherent in his account of laws. The first arises from the juxtaposition of Newton’s confidence in the certainty of his laws and his commitment to their variability and contingency. The second arises because Newton ascribes fundamental status both to the laws and to the bodies and forces they govern. We argue the first is resolvable, but the second is (...) not. However, the second tension shows that Newton conceives laws as formal causes of bodies and forces. This neo-Aristotelian conception goes missing in Kantian accounts of laws, as well as accounts that stress laws’ grounding in powers and capacities. (shrink)

We argue that a conflict between two conceptions of “quantity of matter” employed in a corollary to proposition 6 of Book III of the Principia illustrates a deeper conflict between Newton’s view of the nature of extended bodies and the concept of mass appropriate for the theoretical framework of the Principia. We trace Newton’s failure to recognize the conflict to the fact that he allowed for the justification of natural philosophical claims by two types of a posteriori, empiricist methodologies. Newton's (...) thoughts on these methodologies demonstrate that his natural philosophy continued to develop after the publication of the first edition of Principia and that De Grav should be understood as an early, and not necessarily representative, text. (shrink)

In the history of the scientific revolution, Descartes is often considered as the mechanical philosopher par excellence, and opposed as such to the founder of mechanical science, that is to say, Galileo: this cliché is not without foundation, but it must not make us forget that Descartes was himself a practitioner of mechanical science. In the article "Cartesian Mechanics" I detail the meaning and reach of "mechanics" in the Cartesian corpus, and do so in three steps. 1. I begin by (...) explaining the genesis of the thesis which states that there is no difference between the physical and the mechanical; this thesis is so famous that it is often imagined that it is constituted in Descartes's first writings. But we can in fact show that the first works of Descartes and Beeckman arise from a "physico-mathematical" practice which does not necessarily imply a complete reworking of traditional physics, even if it might have favored the Cartesian ambition for a physics as certain as geometry; it was only in the late 1630s that Descartes began to systematically affirm the identity of physics and mechanics, or of "rules of motion", of "laws of Nature" and of "laws of mechanics". I then analyze the consequences of this affirmation. 2. In the second part of this article I provide a step-by-step commentary of the response proposed by Descartes in a letter to Mersenne in July 1638 to the question raised by Beaugrand's Geostatice (...) dissertatio mathematica (1636), that is to say the question of whether a body weighs more when it is farther from the center of Earth than when it is close. Compared with other texts of the Cartesian corpus, this sample of mechanics has been little analyzed (to my knowledge, the only analyses are those of P. Duhem, P. Costabel, A. Gabbey and D. Garber). This text is nonetheless extremely interesting: Descartes responds to the geostatic question in turn in terms of physics, then mathematics; even more interesting, the examination of the details of his procedures allows us to confront Cartesian statics to other writings, whether those of Guidobaldo del Monte, Galileo, Stevin, Mersenne or Roberval. 3. In the third and final section, I analyze the reasons that lead Descartes to exclude velocity from his statics, I examine the difficulties that his explanation of gravity created for statics, and conclude with the confrontation between mechanical philosophy and mechanical science in the case of Descartes. (shrink)