const TransSet : set prop const In : set set prop term iIn = In infix iIn 2000 2000 term ordinal = \x:set.TransSet x & !y:set.y iIn x -> TransSet y const Sing : set set const ordsucc : set set const Empty : set axiom not_TransSet_Sing1: ~ TransSet (Sing (ordsucc Empty)) claim ~ ordinal (Sing (ordsucc Empty))