Who says internet combox discussions are never fruitful? After almost two weeks of back and forth, Learned Hand has finally come around on the infallibility of the law of identity.
LH before: I cannot therefore be logically, absolutely certain of anything—not even that A=A.
LH today: Defining A as equal to A is defining A as equal to A; the proposition is not fallible if the only metric is its own definition.
Now if we could only convince him that he does not have to doubt whether he is Mount Everest.