>item, so A=A is tautologous. I believe that makes it
>invalid as an axiom, but I have to admit I'm not well
>up on formal systems, and will welcome any comments.
Tautologies (statements that are necessarily true) are
valid axioms. For instance, the inference rules of a
logic system such as (A & B) -> ~(~A v ~B) are tautologous
axioms. Contradictions (statements that are necessarily
false) are invalid axioms.
-- David McFadzean david@lucifer.com Memetic Engineer http://www.lucifer.com/~david/ Church of Virus http://www.lucifer.com/virus/