Full Idea
The Identity of Indiscernibles (no two objects can possess exactly the same properties) is not the same as Leibniz's Law (what is true of a thing is true of what is identical with that thing).
Gist of Idea
Identity of Indiscernibles (same properties, same thing) ) is not Leibniz's Law (same thing, same properties)
Source
E.J. Lowe (A Survey of Metaphysics [2002], p.62)
Book Reference
Lowe,E.J.: 'A Survey of Metaphysics' [OUP 2002], p.62
A Reaction
Two things can't be the same because we can't discern the difference, which may be our inadequacy. But if they actually have identical properties, it is hard to see how they could be different. A universe with just two perfect spheres is couterexample.