SOURCE: "Newton's Theory of Matter," in Isis, Vol. 51, No. 164, June 1960, pp. 131-44.

In the following essay, Hall and Hall examine several of Newton's unpublished manuscripts in order to better understand the development of his theory of matter.

A clear understanding of Newton's real thoughts about the nature of matter and of the forces associated with material particles has always been (to borrow his own phrase) "pressed with difficulties." That a corpuscular or particulate theory was unreservedly adopted by him has long been abundantly evident from many passages in the Principia, and from the Quaeries in Opticks, to mention only discussions fully approved for publication by Newton himself. So far, then, Newton was undoubtedly a "mechanical philosopher" in the spirit of his age, the spirit otherwise expressed, for example, by Boyle and Locke. But of the exact content and form of his mechanical philosophy it is less easy to...