case not_ phi phi_ih =>
  unfold sub at h1
  unfold IsMetaVarOrAllDefInEnv at h1
  unfold IsMetaVarOrAllDefInEnv
  exact phi_ih h1
E : Env
σ : Instantiation
τ : MetaInstantiation
phi : Formula
phi_ih : IsMetaVarOrAllDefInEnv E (sub σ τ phi) → IsMetaVarOrAllDefInEnv E phi
h1 : IsMetaVarOrAllDefInEnv E (sub σ τ phi.not_)
⊢ IsMetaVarOrAllDefInEnv E phi.not_
no goals