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 ordinal : set prop const SNoLev : set set axiom ordinal_SNoLev: !x:set.ordinal x -> SNoLev x = x const ordsucc : set set const SNo : set prop const SNoLe : set set prop term <= = SNoLe infix <= 2020 2020 lemma !x:set.!y:set.ordinal x -> ordinal y -> x iIn ordsucc y -> SNo x -> SNoLev x = x -> x <= y var x:set var y:set hyp ordinal x hyp ordinal y hyp x iIn ordsucc y claim SNo x -> x <= y