(** 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.
(** If two distinct points of a line belong to a plane, then the line belongs to the plane. *)

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.