Abstract

Newton’s famous pronouncement, Hypotheses non fingo, first appeared in 1713, but his anti-hypothetical stance was present as early as 1672. For example, in his first paper on optics, Newton claims that his doctrine of light and colours is a theory, not a hypothesis, for three reasons (1) It is certainly true, because it supported by (or deduced from) experiment; (2) It concerns the physical properties of light, rather than the nature of light; and (3) It has testable consequences. Despite his clear anti-hypothetical statements, a corpuscular hypothesis lies beneath Newton’s theory of colours. What are we to make of this? Is Newton guilty of feigning a hypothesis? Some writers, such as Sabre and Dear, argue that Newton’s Hypotheses non fingo is merely ‘lip-service’ to the dominant methodological tradition. Others, such as Janiak, argue that Newton’s anti-hypotheticalism is a polemic device, designed specifically to oppose his Cartesian and Leibnizian critics. I argue that, despite his corpuscular hypothesis, we should take Newton’s pronouncement as a genuine account of his methodology. I take a fresh look at Newton’s first optical papers in light of the role of hypotheses in the Baconian-experimental tradition in which Newton’s early research was conducted. I argue that Newton is working with a rough but genuine distinction between hypothesis and theory. This distinction is consistent with both the Baconian-experimental method and with his later anti-hypothetical pronouncements. I conclude that Newton did not ‘feign’ the corpuscular hypothesis.