Boscovich Roger Joseph, or Rudjer Josip Boskovic’ (1711–87), Croatian physicist and philosopher. Born of Serbian and Italian parents, he was a Jesuit and polymath best known for his A Theory of Natural Philosophy Reduced to a Single Law of the Actions Existing in Nature. This work attempts to explain all physical phenomena in terms of the attractions and repulsions of point particles (puncta) that are indistinguishable in their intrinsic qualitative properties. According to Boscovich’s single law, puncta at a certain distance attract, until upon approaching one another they reach a point at which they repel, and eventually reach equilibrium. Thus, Boscovich defends a form of dynamism, or the theory that nature is to be understood in terms of force and not mass (where forces are functions of time and distance). By dispensing with extended substance, Boscovich avoided epistemological difficulties facing Locke’s natural philosophy and anticipated developments in modern physics. Among those influenced by Boscovich were Kant (who defended a version of dynamism), Faraday, James Clerk Maxwell, and Lord Kelvin. Boscovich’s theory has proved to be empirically inadequate to account for phenomena such as light. A philosophical difficulty for Boscovich’s puncta, which are physical substances, arises out of their zero-dimensionality. It is plausible that any power must have a basis in an object’s intrinsic properties, and puncta appear to lack such support for their powers. However, it is extensional properties that puncta lack, and Boscovich could argue that the categorial property of being an unextended spatial substance provides the needed basis. J.Ho. & G.Ro.