 Regardless of what form of atomism one endorsed, a common argument in atomism’s favor appeals to the notion of a sensible body’s being an aggregation of parts. The argument is directed against the idea that a continuous magnitude, which for the philosophers included the natural sensible bodies that make up the world, can be potentially divisible ad infinitum (cf. Aristotle, Physics 3.7, 207b16). The most general form of the argument rests on two principles: (1) the impossibility of an actual infinity, a premise that even most Aristotelians accepted; and (2) an analysis of potentiality in terms of an agent’s power, namely, to say that some action φ is potential is to say that there exists an agent who has the power actually to do φ. As part of a reductio-style argument, one is asked to assume (3), bodies are potentially divisible infinitely. In that case, from (2), there must exist some agent (e.g., God) that can actually bring about the division. So let the agent enact the potential division. Either the result is an actually infinite number of parts or a finite number of parts. From (1), recall, an actual infinity is impossible. Therefore, the totality of potential parts that actually can be produced from the division is finite, but it was assumed that they were infinite, a contradiction. Since (1), (2) and (3) are mutually incompatible, one of these assumptions must be false. The atomists point to the assumption of infinite divisibility and a potentially infinite number of parts. Thus, the argument concludes, the parts from which sensible bodies are aggregated must be finite, whether actually or potentially. 