Pierre Gassendi (1592–1655) and his colleagues placed a high value on the new science of the time, which included the heliocentric (sun-centered solar system) theory after the Copernican revolution, the atomic theory holding that the activities of all matter were determined by its smallest particles—or atoms—and a rejection of those parts of the Aristotelian views of science that were in disagreement with these views. Gassendi’s use of skepticism to attack Aristotle, and his use of moderate skepticism to support the new science, therefore made perfect sense. It helped Gassendi’s cause that he was well liked and highly regarded among his colleagues in the Catholic Church, as well as by some of the more extreme skeptics of his day, and that he was careful not to go against Church doctrine. Indeed, while defending the new science on the one hand, and insisting that no scientific knowledge could be certain on the other, Gassendi was able to live and think in both the traditional Catholic world and the new scientific one.