 What imaginable circumstances would tempt us to say that two [disjoint] things were in the same place at the same time? Imagine two rectangular blocks of the same size and shape each moving along a straight path perpendicular to the other. The blocks approach the intersection of the paths at the same time, and apparently neither slows down nor changes its direction. They seem to pass right through one another, and they do this without changing with respect to colour, texture, density, etc. We want to say that we have the same two blocks with which we started. And we do not want to say that either block passed out of existence and was shortly thereafter re-created. Thus we want to say that each block moved along its path without any spatio-temporal discontinuity. And we can say this only if we admit that parts of one block simultaneously occupied the same space as parts of the other block. (1967: 37)