const Sep : set (set prop) set const UnivOf : set set const Empty : set const nat_p : set prop term omega = Sep (UnivOf Empty) nat_p const In : set set prop term iIn = In infix iIn 2000 2000 axiom nat_p_UnivOf_Empty: !x:set.nat_p x -> x iIn UnivOf Empty axiom SepI: !x:set.!p:set prop.!y:set.y iIn x -> p y -> y iIn Sep x p claim !x:set.nat_p x -> x iIn omega