a ≪ A → \A ∀ A, a0. a ≠ A ∨ ¬ □ ⟨a0 := A⟩ (◇ A ≪ a0) ∨ a0 ≠ A, □ ⟨a0 := A⟩ (◇ A ≪ a0), ◇ (a = A ∧ A ≪ a0), a0 = A ⊦