Full Idea
If block a is on block b, it is hard to see how this state of affairs might consist of both 'on top of' and 'beneath'. Surely if the state is a genuine relational complex, there must be a single relation for these relata?
Gist of Idea
A block on top of another contains one relation, not both 'on top of' and 'beneath'
Source
Kit Fine (Neutral Relations [2000], 1)
Book Reference
-: 'Philosophical Review' [-], p.4
A Reaction
He has already shown that if such relations imply their converses, then that gives you two separate relations. He goes on to observe that you cannot pick one of the two as correct, because of symmetry. He later offers the 'vertical placement' relation.