The conventional view of the prehistory of Newton's synthesis in the Principia of his predecessors' work in planetary theory and terrestrial gravitation is still not seriously changed from that which Newton himself chose to impose on his contemporaries at the end of his life. In his own words:‘… the same year ‘1666’ I began to think of gravity extending to ye orb of the Moon & having found out how to estimate the force wth wch [a] globe revolving within a (...) sphere presses the surface of the sphere from Keplers rule of the periodical times of the Planets being in a sesquialterate proportion of their distances from the centers of their Orbs, & having deduced that the forces wch keep the Planets in their orbs must [be] reciprocally as the squares of their distances from the centers about wch they revolve: & thereby compared the force requisite to keep the Moon in her Orb with the force of gravity at the surface of the earth, & found them answer pretty nearly …’. (shrink)

Isaac Newton's closest approach to a system of the world in the critical period 1681–84 is provided in a set of untitled propositions concerning comets. They drastically revise his position maintained against Flamsteed in 1681 and may signal his adoption of a single comet solution for the appearances of 1680/1. Points of agreement and difference with the key pre-Principia texts of 1684–85 are analysed. He shows substantial control of the phenomena of tails which change very little in mechanical detail throughout (...) his subsequent work. An emerging theory of gravitation brings planets, their satellites, and comets under the same laws of motion, yet retains a celestial vortex and includes a singular proposition in lieu of the usual formulation of Keplers area law. The analysis raises questions on a number of issues of recent Newtonian scholarship ranging from his achievement following his correspondence with Robert Hooke in 1679 to his veneration of the wisdom of the ancients. (shrink)

It is here argued that Halley's comet had a more pivotal role than has hitherto been believed in triggering Newton's acceptance of the law of gravity, dispelling his belief in Descartes' theory of vortices. It is found that historians have been unduly prone to credit Newton with dynamical insights at an earlier date than is warranted by the historical documents. A more convincing account of the transition from the period of Newton's alchemical researches of the 1670s to that of his (...) dynamical insights in the 1680s thereby becomes feasible. Acceptance of a principle of rectilinear inertia was a precondition for formulating the law. (shrink)

This paper is in three sections. The first establishes that Newton, in spite of a well-known passage in a letter to Richard Bentley of 1692, did believe in action at a distance. Many readers may see this merely as an act of supererogation, since it is so patently obvious that he did. However, there has been a long history among Newton scholars of allowing the letter to Bentley to over-ride all of Newton’s other pronouncements in favour of action at a (...) distance, with devastating effects on our understanding of related aspects of his physics and his theology. Furthermore, this misconceived scholarly endeavour shows no sign of abating. The second section then offers a historical reconstruction, based on Newton’s writings, of how, when and why he began to accept actions at a distance and make them one of the cornerstones of his physics. Finally, using this chronological account of Newton’s use of actions at a distance, the paper re-assesses the claims of B. J. T. Dobbs that Newton’s important manuscript, De gravitatione et aequipondio fluidorum, was written, not in the late 1660s or early 1670s as was previously supposed, but during the composition of the Principia, in 1684 or 1685.Keywords: Isaac Newton; Action-at-a-distance; Gravity; Force; Aether; Attraction. (shrink)

Isaac Newton is a legendary figure whose mythical dimension threatens to overshadow the actual man.

Presents Newton's unifying idea of gravitation and explains how he converted physics from a science of explanation into a general mathematical system.

Reproduces the text of Newton's dissertation on the nature and properties of light.

Towards the end of his life, Descartes published the first four parts of a projected six-part work, The Principles of Philosophy. This was intended to be the definitive statement of his complete system of philosophy, dealing with everything from cosmology to the nature of human happiness. In this book, Stephen Gaukroger examines the whole system, and reconstructs the last two parts, 'On Living Things' and 'On Man', from Descartes' other writings. He relates the work to the tradition of late Scholastic (...) textbooks which it follows, and also to Descartes' other philosophical writings, and he examines the ways in which Descartes transformed not only the practice of natural philosophy but also our understanding of what it is to be a philosopher. His book is a comprehensive examination of Descartes' complete philosophical system. (shrink)