(** We need a notion of line. *)

Definition Line := @Couple Tpoint.Definition Lin := build_couple Tpoint.Definition IncidentL := fun A l => Col A (P1 l) (P2 l).

(* Specifications: *)
Lemma axiom_line_existence : forall A B, A<>B -> exists l, IncidentL A l /\ IncidentL B l.