  Potter (1977: 92) refines the argument. We say that A is nearer to D than to F because there are more intervening objects between A and F than there are between A and D. Suppose however that between D and F there is no chain of material objects. How is it that we can still say “A is nearer to D than to F”? Potter answers: “In order to provide the material to explain this comparative judgement we must postulate an intervening series of entities, and these must be spatial”. Note that this explains, not the transitivity of directional relations like “to the left of”, but rather the magnitude of distance relations like “near to”. “Near to” is not a transitive relation. It accepts the basic premise that the distance between two objects is measured in terms of the number of intervening entities, and postulates a series of “spatial entities” when there are no material ones present. 