(** Encoding of Russel's paradox *)
(** The boolean negation. *)
(** the set of elements not belonging to itself *)
Definition R : U := g (fun u:U => Not_b (u U u)).

(* Specifications: *)
Lemma not_has_fixpoint : R R = Not_b (R R).
Theorem classical_proof_irrelevance : T = F.
#[deprecated(since = "8.8", note = "Use classical_proof_irrelevance instead.")]
Notation classical_proof_irrelevence := classical_proof_irrelevance.