fact: Definition ForallR2 {T₁ T₂} P₁ P₂ `{@Relativisation T₁ P₁, @Relativisation T₂ P₂} (f : T₁ -> T₂ -> formula) : formula := fun π => exists t₁ : T₁, exists t₂ : T₂, π ∈ ‖Rel (fun t => Rel (f t) t₂) t₁‖.
imports: Bool String Coq.Classes.RelationClasses