intro D I V E a1
Δ : List Formula
F phi : Formula
⊢ ∀ (D : Type) (I : Interpretation D) (V : VarAssignment D) (E : Env),
    (∀ H ∈ [phi], Holds D I V E H) → Holds D I V E phi
Δ : List Formula
F phi : Formula
D : Type
I : Interpretation D
V : VarAssignment D
E : Env
a1 : ∀ H ∈ [phi], Holds D I V E H
⊢ Holds D I V E phi