proposition: Lemma Double b (phi : form b) : [] ⊢C phi -> [] ⊢I (trans phi).
proof: Proof. eapply Double'. Qed.
imports: Undecidability.PCP(PCP Util.PCP_facts) Undecidability.FOL(Deduction.FragmentNDFacts Semantics.Tarski.FragmentFacts Semantics.Tarski.FragmentSoundness Syntax.Core Syntax.Facts) Undecidability.FOL(FOL) Undecidability.Synthetic(Definitions DecidabilityFacts EnumerabilityFacts ReducibilityFacts MoreReducibilityFacts) Undecidability.FOL.Reductions.PCPb_to_FOL Undecidability.PCP.Reductions.PCPb_iff_dPCPb List Undecidability(Shared.ListAutomation)