(** Definition of a line belonging to a plane.
  We say that a line belongs to a plane if every point of the line belongs to the plane. *)

Definition  IncidentLP := fun l p => forall A, IncidentL A l -> IncidentP A p.

Lemma axiom_line_on_plane : forall A B l p, A <> B -> IncidentL A l -> IncidentL B l -> IncidentP A p -> IncidentP B p -> IncidentLP l p.