I am reading Doubt Truth to be a Liar by Graham Priest. In it he uses the symbol
? as a logical connective, and I am unsure of it's meaning.
Given his use of
? (a ? a) to denote the Law of Identity, my first guess would be that it's a stand in for
=, but the usage also seems to imply that it has at least two parities (1 & 2). I'm stuck.