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 Repl : set (set set) set const Inj1 : set set term Inj0 = \x:set.Repl x Inj1 const Unj : set set var x:set var y:set var z:set var w:set hyp y = Unj z hyp w iIn x hyp z = Inj1 w claim y = w -> y iIn x