In contrast with some recent theories of infinitesimals as non-Archimedean entities, Leibniz’s mature interpretation was fully in accord with the Archimedean Axiom: infinitesimals are fictions, whose treatment as entities incomparably smaller than finite quantities is justifiable wholly in terms of variable finite quantities that can be taken as small as desired, i.e. syncategorematically. In this paper I explain this syncategorematic interpretation, and how Leibniz used it to justify the calculus. I then compare it with the approach of Smooth Infinitesimal Analysis, (...) as propounded by John Bell. I find some salient differences, especially with regard to higher-order infinitesimals. I illustrate these differences by a consideration of how each approach might be applied to propositions of Newton’s Principia concerning the derivation of force laws for bodies orbiting in a circle and an ellipse. “If the Leibnizian calculus needs a rehabilitation because of too severe treatment by historians in the past half century, as Robinson suggests (1966, 250), I feel that the legitimate grounds for such a rehabilitation are to be found in the Leibnizian theory itself.”—(Bos 1974–1975, 82–83). (shrink)

Isaac Newton is best known as a mathematician and physicist. He invented the calculus, discovered universal gravitation and made significant advances in theoretical and experimental optics. His master-work on gravitation, the Principia, is often hailed as the crowning achievement of the scientific revolution. His significance for philosophers, however, extends beyond the philosophical implications of his scientific discoveries. Newton was an able and subtle philosopher, working at a time when science was not yet recognized as an activity distinct from philosophy. He (...) engaged with the work of Rene Descartes and G.W. Leibniz, and showed sensitivity to the work of John Locke, Francis Bacon, Pierre Gassendi and Henry More, to name just a few. In his time, Newton was not perceived as a scientific outsider, but as an active and knowledgeable participant in philosophical debates.... (shrink)

This article casts light on the intimate relationship between metaphysics and science in Adam Smith’s thought. Understanding this relationship can help in resolving an enduring dispute or misreading concerning the status and role of natural theology and the ‘invisible hand’ doctrine. In Smith’s scientific realism, ontological issues are necessary prerequisites for scientific inquiry, and metaphysical ideas thus play an organizing and regulatory role. Smith also recognized the importance of scientifically informed metaphysics in science’s historical development. In this sense, for Smith, (...) the metaphysico-scientific link, was a basic criterion of scientific validation by Inference to the Best Explanation. Furthermore, Smith’s comments implicitly suggest that in scientific progress there is a dialectic between metaphysics and science. These themes are illustrated primarily through his writings on the history of astronomy. (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)

Newton characterizes the reasoning of Principia Mathematica as geometrical. He emulates classical geometry by displaying, in diagrams, the objects of his reasoning and comparisons between them. Examination of Newton’s unpublished texts shows that Newton conceives geometry as the science of measurement. On this view, all measurement ultimately involves the literal juxtaposition—the putting-together in space—of the item to be measured with a measure, whose dimensions serve as the standard of reference, so that all quantity is ultimately related to spatial extension. I (...) use this conception of Newton’s project to explain the organization and proofs of the first theorems of mechanics to appear in the Principia. The placementof Kepler’s rule of areas as the first proposition, and the manner in which Newton proves it, appear natural on the supposition that Newton seeks a measure, in the sense of a moveable spatial quantity, of time. I argue that Newton proceeds in this way so that his reasoning can have the ostensive certainty of geometry. (shrink)