Lean4
/-- If `f` is unsatisfiable, and every `v` which agrees with `ps` implies `¬⟦f⟧_v → p`, then `p`.
Equivalently, there exists a valuation `v` which agrees with `ps`,
and every such valuation yields `¬⟦f⟧_v` because `f` is unsatisfiable. -/
theorem refute {p : Prop} {ps} (f : Fmla) (hf : f.proof []) (hv : ∀ v, Valuation.implies v (Fmla.reify v f p) ps 0) :
p :=
(Valuation.mk_implies [] rfl (hv _)).1 (hf _)