 Atomism was challenged by Aristotle (384–322 BCE), who was the first to undertake the systematic analysis of continuity and discreteness. A thoroughgoing synechist, he maintained that physical reality is a continuous plenum, and that the structure of a continuum, common to space, time and motion, is not reducible to anything else. His answer to the Eleatic problem was that continuous magnitudes are potentially divisible to infinity, in the sense that they may be divided anywhere, though they cannot be divided everywhere at the same time.