Full Idea
It seems to me that the Leibnizian principle of the indiscernibility of identicals (not to be confused with the identity of indiscernibles) is as self-evident as the law of contradiction.
Gist of Idea
The indiscernibility of identicals is as self-evident as the law of contradiction
Source
Saul A. Kripke (Naming and Necessity preface [1980], p.03)
Book Reference
Kripke,Saul: 'Naming and Necessity' [Blackwell 1980], p.3
A Reaction
This seems obviously correct, as it says no more than that a thing has whatever properties it has. If a difference is discerned, either you have made a mistake, or it isn't identical.