‘Though their causes be not yet discover’d’: occult principles in the making of Newton’s natural philosophy

This thesis aims to provide a fuller understanding of a highly important but still controversial aspect of Isaac Newton’s natural philosophy: the role of occult, or at least non-mechanical, principles in his natural philosophy. The most obvious of these was his belief that gravity was an attractive force which operated across empty space, and so was an occult actio in distans. But there are other aspects of Newton’s work which would have been regarded by Cartesian contemporaries as occult; such as his belief that light can be an active component within bodies, that light and other matter can be converted into one another, and that bodies are not inert and passive but manifest various principles of activity. R. S. Westfall, suggested in the 1970s that Newton’s unprecedented success as a natural philosopher was due to the fact that he combined two seemingly antithetical traditions of natural knowledge, the mechanical tradition, and what he called the Hermetic tradition. This thesis replaces Westfall’s outdated notion of a “Hermetic” tradition with broader occult or natural magical traditions and shows how they formed the context within which Newton’s own work was formed. The thesis is not primarily a study of Newton’s work but a study of the work of earlier English thinkers who can be seen to have established the occult traditions which were subsequently taken up by Newton. Each chapter, therefore, focuses on a different aspect of occult ways of thinking in natural philosophy during the early modern period, and finally shows, in the conclusion to each chapter, how these ideas appeared in Newton’s work, and, as Westfall suggested, contributed to his unprecedented success. Over six chapters the thesis considers theories that the world system is a network of radiating forces analogous to light rays, that gravity is an attractive force analogous to magnetism and operates at a distance, that matter has the power to attract and repel other matter, or has the power to incessantly emit active material effluvia, or the power to vibrate. It also shows how beliefs about the mathematical principles of natural philosophy, and the usefulness of the experimental method made possible, and supported, these theories about occult principles. The focus is on English thinkers and developments in English natural philosophy. This is not just an arbitrary choice but reflects sympathetic attitudes to occult ways of thinking in English thought which are shown to derive from the first natural philosophers in England to acquire international reputations since the Middle Ages, John Dee, Francis Bacon, and William Gilbert. Writing before the mechanical philosophy was conceived, these three thinkers all embraced occult ideas and left them as a legacy for subsequent English thinkers, up to and including Newton. The thesis shows that the combination of occult and mechanical traditions discerned in Newton’s work by Westfall was in fact highly typical of English thinkers who combined occult ideas deriving from Dee, Bacon, and Gilbert, with the emerging mechanical philosophy. This marked trend in English natural philosophy reached its culminating point in the work of Newton, but Newton’s achievement was only possible because of what had gone before. The thesis shows, therefore, that Newton’s achievement crucially depended upon this English background