Modal substitution theorem If Ω;⋅ ⊢ π1 : A and Ω, u: (A valid) ; Γ ⊢ π2 : C, then Ω;Γ ⊢ [π1/u] π2 : C.
Modal substitution th:eorem If Ω;⋅ ⊢ π1 : A and Ω, u (A valid) ; Γ ⊢ π2 : C, then Ω;Γ ⊢ [π1/u] π2 : C.