Instance Hilbert_3D_follows_from_Tarski_3D : Hilbert_neutral_3D Hilbert_neutral_follows_from_Tarski_neutral.(** * Group Parallels *)

Definition Para := fun l m =>
  (~ exists X, IncidentL X l /\ IncidentL X m) /\ exists p, IncidentLP l p /\ IncidentLP m p.

Lemma Para_Par : forall A B C D (HAB : A<>B) (HCD: C<>D), Para (Lin A B HAB) (Lin C D HCD) -> Par A B C D.