 Locke and Newton also share the problem of an evidentiary deficit, insofar as they subscribe to corpuscularianism. Thinkers who did subscribe tended to rely on transduction (also called transdiction)--an inductive inference that is empirical insofar as it relies upon observed cases, but which generalizes not only to unobserved cases but to ones that are unobservable.[23])  Newton’s Rule 3 licensed such inferences, from the Principia’s second edition onward, for qualities of invariable intensity, i.e., extension, impenetrability, hardness, mobility, and the vis inertiae. The rule is explicit in permitting inferences to the realm of the unobservable: “Because the hardness of the whole arises from the hardness of the parts, we justly infer from this not only the hardness of the undivided particles of bodies that are accessible to our senses, but also of all other bodies.”(Principia, Book 3, p. 795.[24] ) As for Locke and the problem of transduction, how serious it is for him depends largely upon the status of the corpuscular hypothesis. If he takes an agnostic or skeptical stance toward it, then he owes no solution to the problem. 