Full Idea
As a necessary condition of the truth of an identity claim, some common sort f will have to be found to which they each belong. That is the point at which the primary question of identity can come into focus.
Gist of Idea
To identify two items, we must have a common sort for them
Source
David Wiggins (Sameness and Substance Renewed [2001], 2.2)
Book Reference
Wiggins,David: 'Sameness and Substance Renewed' [CUP 2001], p.58
A Reaction
This is the plainest English expression I can find of Wiggins's main thesis. He maintains this thesis, while adamantly denying the idea that identity consists entirely of falling under a concept.