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 Empty : set const ordsucc : set set axiom In_0_1: Empty iIn ordsucc Empty axiom ordsuccI1: !x:set.Subq x (ordsucc x) claim Empty iIn ordsucc (ordsucc Empty)