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 term nIn = \x:set.\y:set.~ x iIn y const Empty : set const ordsucc : set set axiom In_0_1: Empty iIn ordsucc Empty const SNoLev : set set const SNo : set prop var x:set hyp SNo x hyp SNoLev x iIn ordsucc Empty claim Empty = x -> x iIn ordsucc Empty