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 term TransSet = \x:set.!y:set.y iIn x -> Subq y x const Pi : set (set set) set term setexp = \x:set.\y:set.Pi y \z:set.x const SNo : set prop const SNoLt : set set prop term < = SNoLt infix < 2020 2020 term SNoCutP = \x:set.\y:set.(!z:set.z iIn x -> SNo z) & (!z:set.z iIn y -> SNo z) & !z:set.z iIn x -> !w:set.w iIn y -> z < w term nIn = \x:set.\y:set.~ x iIn y const omega : set const SNoLe : set set prop term <= = SNoLe infix <= 2020 2020 const ap : set set set const ordsucc : set set lemma !x:set.!y:set.!z:set.!w:set.(!u:set.u iIn omega -> ap x u <= ap y u & ap x u <= ap x (ordsucc u) & ap y (ordsucc u) <= ap y u) -> (!u:set.u iIn omega -> SNo (ap x u)) -> (!u:set.u iIn z -> ap x u <= ap x z) -> w iIn ordsucc z -> z iIn omega -> ordsucc z iIn omega -> w iIn omega -> ap x z <= ap x (ordsucc z) -> ap x w <= ap x (ordsucc z) var x:set var y:set var z:set var w:set hyp !u:set.u iIn omega -> ap x u <= ap y u & ap x u <= ap x (ordsucc u) & ap y (ordsucc u) <= ap y u hyp !u:set.u iIn omega -> SNo (ap x u) hyp !u:set.u iIn z -> ap x u <= ap x z hyp w iIn ordsucc z hyp z iIn omega hyp ordsucc z iIn omega claim w iIn omega -> ap x w <= ap x (ordsucc z)