In this paper I interpret Newton's speculative treatment of gravity as a relational, accidental property of matter that arises through what Newton calls “the shared action” of two bodies of matter. In doing so, I expand and extend on a hint by Howard Stein. However, in developing the details of my interpretation I end up disagreeing with Stein's claim that for Newton a single body can generate a gravity/force field. I argue that when Newton drafted the first edition of the Principia in the mid 1680s, he thought that (at least a part of) the cause of ...

Newton's development of an ontology of force, along with a mathematical treatment of natural phenomena, had vexed both historians and philosophers of science for decades. In dealing with such a dilemma, philosophers of science and Whig historians more often than not adopt a positivist stance which stresses Newton's agnosticism towards the causation of force, and highlight some sort of positivism in his natural philosophy, thus downplaying his ontological commitments to the conundrum of causation of force. On the other hand, contextualist historians tackle that puzzle by making use whether of Newton's alchemical studies or his metaphysics of nature founded upon a voluntaristic theology, in order to assert Newton's involvement in harmonizing his mathematical physics and natural philosophy within the framework of British natural philosophy. Notwithstanding this, Newton's philosophy of mathematics, and especially his ontology of mathematical entities, remains outside the sphere of interests for both historians and philosophers of science. The aim of this thesis is to rehearse an approach to the problem of Newton's ontology of force by analyzing his ontology of mathematical entities, as deployed in the Principia, within the framework of Newton's voluntarist theology. The purpose is that of showing that within Newton's own mathematical practice we are not required to mingle levels of his epistemological discourse with his ontological assumptions as it happens in the above-mentioned approaches. By means of this analysis, it is expected, additionally, to advance our understanding of Newton's acceptance of action at a distance based upon his notion of gravity force as a superadded quality.

I argue that Isaac Newton's _De Gravitatione_ should not be considered an authoritative expression of his thought about the metaphysics of space and its relation to physical inquiry. I establish the following narrative: In _De Gravitatione_ (circa 1668--1684), Newton claimed he had direct experimental evidence for the work's central thesis: that space had ``its own manner of existing'' as an affection or emanative effect. In the 1710s, however, through the prodding of both Roger Cotes and G. W. Leibniz, he came to see that this evidence relied on assumptions that his own _Principia_ rendered unjustifiable. Consequently, he (i) revised the conclusions he explicitly drew from the experimental evidence, (ii) rejected the idea that his spatial metaphysics was grounded in experimental evidence, and (iii) reassessed the epistemic status of key concepts in his metaphysics and natural philosophy. The narrative I explore shows not only that _De Gravitatione_ did not constitute the metaphysical backdrop of the _Principia_ as Newton ultimately understood it, but that it was the _Principia_ itself that ultimately lead to the demise of key elements of _De Gravitatione_. I explore the implications of this narrative for Andrew Janiak's and Howards Stein's interpretations of Newton's metaphysics.

It is argued that the sensorium of God was introduced into the Quaestiones added to the end of Newton's Optice (1706) as a way of answering objections that Newton had failed to provide a causal account of gravity in the Principia. 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.