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 SNo : set prop const SNoR : set set const Empty : set lemma !x:set.ordinal x -> SNo x -> SNoLev x = x -> SNoR x = Empty var x:set hyp ordinal x claim SNo x -> SNoR x = Empty