Newton, active powers, and
the mechanical philosophy
Among the notable eighteenth-century expositions of Newton's achievements were Henry Pemberton's A View of Sir Isaac Newton's Philosophy (1728), Willem Jacob 'sGravesande's Mathematical Elements of Natural Philosophy confirm'd by experiments: or, an introduction to Sir Isaac Newton's Philosophy (6th edn, 1747), and Colin Maclaurin's posthumous An Account of Sir Isaac Newton's Philosophical Discoveries (1748). To the modern eye, there is something puzzling about these titles. We note the terms “philosophy, ” “natural philosophy, ” and “philosophical, ” and we wonder what they mean in this setting. Take Maclaurin's Account, the best of the genre, and written by one of the leading Newtonians of the day. Newton made great scientific discoveries, and we can learn what most of them are from reading An Account, but what philosophical discoveries did he make? Maclaurin describes Newton's work in mechanics, rational and celestial, and in physics, theoretical and experimental (though not optics). But Newton the philosopher? To answer these questions requires a preliminary disentanglement of the disciplinary classifications that clustered around the business of “philosophy” in the seventeenth and eighteenth centuries.
In Newton's day the predominant framework of university instruction in philosophy was that of the Peripatetic or scholastic tradition, adapted to local religious and cultural requirements (Protestant in Germany, Holland, and Britain; Catholic in France, Spain, and Italy). In that tradition, Philosophy divides into speculative and practical philosophy. Speculative philosophy divides in turn into three principal sciences (scientiae):metaphysics or first philosophy, natural philosophy, and mathematics; to which are added the middle sciences (scientiae mediae), which include theoretical