Full Idea
A counterpart relation is a similarity relation. Since there are different dimensions of similarity, there are different counterpart relations.
Gist of Idea
Counterparts rest on similarity, so there are many such relations in different contexts
Source
Theodore Sider (Four Dimensionalism [2001], 6.4)
Book Reference
Sider,Theodore: 'Four Dimensionalism' [OUP 2003], p.223