metalanguage natural deduction presburger arithmetic formal proof fast-growing hierarchy feferman– schütte ordinal large countable ordinal ω-consistent theory sequent veblen function cut-elimination theorem ordinal analysis epsilon calculus pure type system independence (mathematical logic) setoid system u lambda-mu calculus dialectica interpretation proof calculus realizability conservative extension structural rule church– kleene ordinal double-negation translation gödel's speed-up theorem bounded quantifier bachmann– howard ordinal structural proof theory ordinal notation
Mathematics_Mathematical proofs