Module Type Protothetic (dolce:DOLCE_root).
(************************** Meta-rules of Protothetic in Coq ***************************)
Parameter eqP : Prop -> Prop -> Prop.
Notation "a ≡≡ b" := (eqP a b)  (at level 80).
(* elimination rules for equivalence *)
Parameter detachL     : forall (p q:Prop), (p ≡≡ q) -> p -> q.
Parameter detachR     : forall (p q:Prop), (p ≡≡ q) -> q -> p.
(* substitution rules for equivalence -> use rewrite *)

Lemma T4 : forall p q:Prop, ((p ≡≡ q) ≡≡ (q ≡≡ p)). (* symmetry in Proto *)