  This explanation has a problem. It assumes that between any two bodies there is a chain of touching material objects. But, given this assumption, we do not need to postulate a new substance with which everything is in contact, in order to create a transitive relation from contact. For we can define “being to the left of” thus: x is to the left of y iff there are distinct objects p, q, r,…t such that x is in contact with p, p is in contact with q, …, t is in contact with y.