  It is not clear, however, in what sense the atoms are said to be indivisible, and how the need for smallest magnitudes is related to the claim that atoms are indivisible.  Furley suggests that the atomists may not have distinguished between physical and theoretical indivisibility of the atoms (Furley 1967, p. 94).  The physical indivisibility of the atoms seems to be independent of the argument for indivisible magnitudes, since the solidity of atoms—the fact that there is no void within them—is said to be the reason why they cannot be split.  The existence of void space between atoms is cited as the reason why they can be separated: one late source, Philoponus, even suggests that atoms could never actually touch, lest they fuse (DK 67A7).  Whether or not Democritus himself saw this consequence, it seems that atoms are taken to be indivisible whatever their size.  Presumably, though, there is a smallest size of atom, and this is thought to be enough to avoid the paradoxes of infinite divisibility.