const ordinal : set prop const In : set set prop term iIn = In infix iIn 2000 2000 axiom ordinal_Hered: !x:set.ordinal x -> !y:set.y iIn x -> ordinal y const SNoLt : set set prop term < = SNoLt infix < 2020 2020 lemma !x:set.!y:set.ordinal x -> y iIn x -> ordinal y -> y < x claim !x:set.ordinal x -> !y:set.y iIn x -> y < x