Mechanism is the view that the material world is composed of small particles (corpuscles, or atoms), whose motion, size, shape, and various arrangements and clusterings provide the theoretical background for the explanation of all happenings in the physical universe. Early modern authors, whether mechanists or not, assumed that the matter composing these particles was one and the same throughout the universe. With very few exceptions, they also assumed that there were immaterial entities such as human minds (or souls) and angels.
This view, which became the dominant one during the seventeenth century, had earlier precursors, both in classical times and in the Renaissance period, but the major earlier view, following Aristotle, explained the behaviour of material things in virtue of their form or nature: snow was white because it was the kind of thing that was white: it was the nature of snow to be white.
By this ‘way of dispatching difficulties, they make it very easy to solve All the Phænomena of Nature in Generall, but make men think it impossible to explicate almost Any of them in Particular’, said Robert Boyle, adding that it was only the ‘Comprehensive Principles of the Corpuscularian Philosophy’ which would allow unmysterious explanations of physical phenomena (Boyle 1999, 5: 300–1).
However, many of the things mechanism was invoked to explain – gravity and magnetism, for example – remained inexplicable on simple mechanistic accounts. Nonetheless, one important and lasting result of ‘the mechanical philosophy’ was the acceptance of the requirement that all explanations be understandable, that is, explicable in terms of elementary particles and their motion. In the hands of thinkers such as Galileo, Descartes, Boyle, and Newton this led to a reliance on experience and experiment, often controlled and quantified experiments, in place of the older, Aristotelian, model which viewed science as involving the deduction of necessary, universal, truths, from premises which were themselves necessary.
An account of a book, very lately publish't, entituled, The origine of forms and qualities, illustrated by considerations and experiments, by the Honourable Robert Boyle