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 SNo : set prop axiom ordinal_SNo: !x:set.ordinal x -> SNo x const SNoL : set set const SNoS_ : set set lemma !x:set.ordinal x -> SNo x -> SNoL x = SNoS_ x claim !x:set.ordinal x -> SNoL x = SNoS_ x