Full Idea
The relations which are featured in criteria of identity are always equivalence relations.
Clarification
An equivalence relation is transitive, symmetric and reflexive
Gist of Idea
The relations featured in criteria of identity are always equivalence relations
Source
Bob Hale (Abstract Objects [1987], Ch.3.III)
Book Reference
Hale,Bob: 'Abstract Objects' [Blackwell 1987], p.57
A Reaction
This will only apply to strict identity. If I say 'a is almost identical to b', this will obviously not be endlessly transitive (as when we get to k we may have lost the near-identity to a). Are 'two threes' identical to 'three twos'?