proposition: Lemma valid_satis phi : valid phi -> ~ satis (¬ phi).
proof: Proof. intros H1 (D & I & rho & H2). apply H2, (H1 D I rho). 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.PCP.Reductions.PCPb_iff_dPCPb Undecidability(Shared.ListAutomation)