ArgumentIt is argued that the sensorium of God was introduced into theQuaestionesadded to the end of Newton’sOptice(1706) as a way of answering objections that Newton had failed to provide a causal account of gravity in thePrincipia. The discussion of God’s sensorium indicated that gravity must be caused by God’s will. Newton did not leave it there, however, but went on to show how God’s will created active principles as secondary causes of gravity. There was nothing unusual in assuming that God, (...) acting as the First Cause, operated in nature by means of secondary causes; but it was unusual to devote as much time to discussing God’s precise role as to discussing the secondary causes themselves. It is contended that Newton felt the need to do this to persuade readers that what might seem like a second cause that could not possibly work could be made to work by the omnipotent God. (shrink)

Samuel Clarke is best known to historians of science for presenting Isaac Newton’s views to a wider audience, especially in his famous correspondence with G. W. Leibniz. Clarke’s independent writings, however, reveal positions that do not derive from, and do not coincide with, Newton’s. This essay compares Clarke’s and Newton’s ideas on the cause of gravity, with a view to clarifying our understanding of Newton’s views. There is evidence to suggest that Newton believed God was directly responsible for gravity, and (...) this interpretation has been promoted by a number of scholars. By comparing Newton’s views with those of Clarke, however, it can be seen that Newton did not subscribe to the kind of occasionalist approach to gravity that Clarke developed. Clarke insisted that matter was categorically incapable of being endowed with powers or forces and that therefore what looks like gravitational attraction has to be performed directly by God or by angels. By comparing Clarke’s pronouncements with Newton’s, it becomes clear that Newton adopted the more standard line: that the first cause, God, operated in nature through secondary causes and that gravitational attraction was just such a secondary (albeit occult) cause. (shrink)

The correspondence in 1680 and 1681 between John Flamsteed and Isaac Newton on Flamsteed’s theory of the comet of 1680 tells half the story. Related manuscripts reveal Newton was pursuing his own comprehensive line of inquiry based on principles that were the antithesis of Flamsteed’s procedures. Following generally accepted views in England, Newton’s work was marked by critical evaluation of data but marred by uncritical use of simple calculating techniques based on what might be termed Platonic archetypes of straightness. Flamsteed’s (...) intervention provided useful data and allowed Newton to seek additional information. Although Newton supposedly briefly considered a solution that vaguely resembled his parabolic approximation of the path of the comet determined 5 years later, the evidence Newton provided (based on simple hypotheses) did not support such a highly curved path or one in which the sun apart from the solar vortex exerted influence. Newton’s work, including an alleged harmonic law of tails, was quietly abandoned in favor of other work. With new insight, Newton revived work on comets as fully gravitational objects immediately following Halley’s visit in 1684. This little known side of the episode provides a fresh opportunity to examine Newton’s sources and actual practice in developing a new line of inquiry. An appendix dating sections of Newton’s Waste Book entries on comets is included. (shrink)