Force, matter, and metaphysics in Newton's natural philosophy Public Deposited

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  • March 20, 2019
  • Kochiras, Hylarie
    • Affiliation: College of Arts and Sciences, Department of Philosophy
  • Metaphysical principles may be intuitively appealing by making the world intelligible, yet they are very difficult to justify. The role that such principles should play in the development of a physical theory becomes a pressing question for Newton, for he seeks a causal explanation of gravity that will eliminate the spectre of matter acting at distance, with sun and planets attracting one another across empty space. Does Newton reach an answer to his question about gravity's causal story, and if not, what stands in the way? Despite his empiricism, he is strongly drawn to the metaphysical principles that matter is passive and that causation is local, so at one level, his problem about gravity seems to be that of discovering some immaterial medium that might possess active powers. Yet I identify in Newton's reasoning a more fundamental problem about gravity, Newton's Substance Counting Problem. His ontology includes immaterial substances as well as material ones, and while his penchant for certain metaphysical principles keeps the search for an immaterial medium alive, his empiricism prevents him from postulating such a medium. He also allows, on empirical grounds, the possibility that substances of different kinds can co-occupy regions of space. Yet if two things can be in the same place at the same time, I argue, Newton has no empirical means of determining how many substances are present on the basis of perceived properties, or of associating those properties with one substance rather than another. Nor will he make those determinations by asserting the metaphysical principles he suspects to be true. Thus he has no means of associating active powers with an immaterial medium rather than with matter, and Newton's problem of discovering gravity's complete causal story is one that cannot be solved.
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  • Nelson, Alan Jean
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