Library Coq.Logic.PropExtensionality

This module states propositional extensionality and draws consequences of it

Axiom propositional_extensionality :
  forall (P Q : Prop), (P <-> Q ) -> P = Q.

Require Import ClassicalFacts.

Theorem proof_irrelevance : forall (P:Prop) (p1 p2:P), p1 = p2.
Proof.
  apply ext_prop_dep_proof_irrel_cic.
  exact propositional_extensionality.
Qed.