Full Idea
Identity propositions are not always analytic or a priori (as Frege long ago taught us) so there is nothing trivial about such propositions; the claim of redundancy ignores the epistemic role that the concept of identity plays.
Gist of Idea
Identity propositions are not always tautological, and have a key epistemic role
Source
Colin McGinn (Logical Properties [2000], Ch.1)
Book Reference
McGinn,Colin: 'Logical Properties' [OUP 2003], p.13
A Reaction
He is referring to Frege's Morning Star/Evening Star distinction (Idea 4972). Wittgenstein wanted to eliminate our basic metaphysics by relabelling it as analytic or tautological, but his project failed. Long live metaphysics!
Related Idea
Idea 4972 I may regard a thought about Phosphorus as true, and the same thought about Hesperus as false [Frege]