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 binintersect : set set set axiom binintersectI: !x:set.!y:set.!z:set.z iIn x -> z iIn y -> z iIn binintersect x y claim !x:set.!y:set.!z:set.Subq z x -> Subq z y -> !w:set.w iIn z -> w iIn binintersect x y