(** The following proof comes from [[ChicliPottierSimpson02]] *)

(* Specifications: *)
Theorem classic_set_in_prop_context :
forall C:Prop, ((forall P:Prop, {P} + {~ P}) -> C) -> C.
Corollary not_not_classic_set :
((forall P:Prop, {P} + {~ P}) -> False) -> False.