const In : set set prop term iIn = In infix iIn 2000 2000 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 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 Sep : set (set prop) set const SNoS_ : set set const SNoLev : set set term SNoL = \x:set.Sep (SNoS_ (SNoLev x)) \y:set.y < x term SNoR = \x:set.Sep (SNoS_ (SNoLev x)) (SNoLt x) term ordinal = \x:set.TransSet x & !y:set.y iIn x -> TransSet y const SNoCut : set set set axiom SNoCutP_SNoCut_R: !x:set.!y:set.SNoCutP x y -> !z:set.z iIn y -> SNoCut x y < z const Repl : set (set set) set const minus_SNo : set set term - = minus_SNo var x:set var y:set hyp SNoCutP (Repl (SNoR x) minus_SNo) (Repl (SNoL x) minus_SNo) hyp y iIn Sep (SNoS_ (SNoLev x)) \z:set.z < x claim - y iIn Repl (SNoL x) minus_SNo -> SNoCut (Repl (SNoR x) minus_SNo) (Repl (SNoL x) minus_SNo) < - y