Axiom unfold_Rstar: (P:(A->A->Prop)->Prop)
(P [x,y:A](P0:A->A->Prop)
((u:A)(P0 u u))
->((u:A)(v:A)(w:A)(R u v)->(P0 v w)->(P0 u w))->(P0 x y))
->(P Rstar).