intro N
W : Type
M : KripkeModel W
w : W
⊢ ∀ {N : ℕ} (XS : List (List Formula)), XS.length = N → (evaluate M w (discon XS) ↔ ∃ Y ∈ XS, ∀ f ∈ Y, evaluate M w f)
W : Type
M : KripkeModel W
w : W
N : ℕ
⊢ ∀ (XS : List (List Formula)), XS.length = N → (evaluate M w (discon XS) ↔ ∃ Y ∈ XS, ∀ f ∈ Y, evaluate M w f)