structural rules 1.Γ, 𝐴, 𝐴 ⊢ Σ Γ, 𝐴 ⊢ Σ Γ, A, A ⊢ Σ <div class="den">Γ, A ⊢ Σ </div> Γ, A, A ⊢ Σ <div class="den">Γ, A ⊢ Σ </div>contractionrule✹ 2.Γ ⊢ Σ Γ, 𝐴 ⊢ Σ Γ ⊢ Σ <div class="den">Γ, A ⊢ Σ </div> Γ ⊢ Σ <div class="den">Γ, A ⊢ Σ </div>weakeningrule✹ 3.𝐴, 𝐵 ⊢ Σ 𝐵, 𝐴 ⊢ Σ A, B ⊢ Σ <div class="den">B, A ⊢ Σ </div> A, B ⊢ Σ <div class="den">B, A ⊢ Σ </div>permutationrule✹