aesop
ν : Type u_1
τ : PropAssignment ν
x : ν
φ φ₁ φ₂ φ₃ : PropForm ν
⊢ ((∀ (τ : PropAssignment ν), τ ⊨ φ₁ → τ ⊨ φ₂) ∧ ∀ (τ : PropAssignment ν), τ ⊨ φ₂ → τ ⊨ φ₁) ↔
    ∀ (τ : PropAssignment ν), τ ⊨ φ₁ ↔ τ ⊨ φ₂
no goals