Discusses Hobbes's relationship with the French mathematician Gilles Personne de Roberval, with whom he became closely associated in Paris during the 1640s. It examines a text that, commonly assumed to be a statement of Roberval's own views, may rather have been a description (adapted in some ways by Roberval) of the views of Hobbes. The degree to which Hobbes and Roberval were able to assimilate elements of skepticism is also discussed, particularly in relation to the different ways in which they reacted to the experimental evidence for the production of a vacuum in the late 1640s.
Keywords: Gassendi, Hobbes, Roberval, skepticism, vacuum