const In : set set prop term iIn = In infix iIn 2000 2000 term Subq = \x:set.\y:set.!z:set.z iIn x -> z iIn y const ordsucc : set set axiom ordsuccI2: !x:set.x iIn ordsucc x var x:set var y:set hyp Subq x y hyp Subq y x claim x = y -> x iIn ordsucc y