Full Idea
When we consider the semantic role of 'x' and 'y' in two distinct expressions x>0 and y>0, their semantic roles seems the same. But in the same expression, such as x>y, their roles seem to be different.
Gist of Idea
In separate expressions variables seem identical in role, but in the same expression they aren't
Source
Kit Fine (Semantic Relationism [2007], 1.A)
Book Reference
Fine,Kit: 'Semantic Relationism' [OUP 2007], p.7
A Reaction
[compressed] This new puzzle about variables leads Fine to say that the semantics of variables, and other expressions, is not intrinsic to them, but depends on their external relations. Variables denote any term - unless another variable got there first.