obtain ⟨X, hX₁, hX₂⟩ := by simpa using ConverseWellFounded.iff_has_max.not.mp hCF;
W α : Type u
inst✝¹ : Inhabited W
inst✝ : Inhabited α
F : Frame' α
hCF : ¬ConverseWellFounded F.Rel
⊢ ¬F ⊧* 𝗟
case intro.intro
W α : Type u
inst✝¹ : Inhabited W
inst✝ : Inhabited α
F : Frame' α
hCF : ¬ConverseWellFounded F.Rel
X : Set F.World
hX₁ : X.Nonempty
hX₂ : ∀ x ∈ X, ∃ x_1 ∈ X, F.Rel x x_1
⊢ ¬F ⊧* 𝗟