 The most difficult problem for atomists arises from book VI of Aristotle’s Physics, where it becomes necessary to define the contiguity of atoms. Since an atom by definition has no parts, how can we say that they touch each other? If they are actually in contact, they should be in one and the same place (if not, then there is no continuity since continuity requires contiguity). Crathorn replies by saying that this is a problem only for those who think of atoms as mathematical points. But since he holds that atoms have a proper magnitude and that they are defined by the fact that they occupy a single location (situs or locus), a quantity that is simply the place occupied by the quantified thing (I Sent., qq. 3 and 14–15), the contiguity and continuity of atoms can be explained in terms of the contiguity of places. Atoms can form a continuous magnitude if all of them are contiguous, i.e., if they all occupy contiguous atomic places.