Full Idea
Not every (apparent) judgement of identity involves application of anything properly describable as a criterion of identity, ...such as being able to pronounce that mercy is the quality of being merciful.
Gist of Idea
We sometimes apply identity without having a real criterion
Source
Bob Hale (Abstract Objects [1987], Ch.2.II)
Book Reference
Hale,Bob: 'Abstract Objects' [Blackwell 1987], p.39
A Reaction
This suggests some distinction between internal criteria (e.g. grammatical, conceptual) and external criteria (existent, sensed).