It is evident that both of the new eigenstates are superposition of the original degenerate eigenstates and one of the eigenvalues (here E − − ) is less than the original unperturbed eigenenergy. So the corresponding stable system will naturally mix up the former unperturbed eigenstates to minimize its energy. In the example of benzene the experimental evidences of probable bond structures give rise to two different eigenstates, | ψ ψ 1 ⟩ ⟩ and | ψ ψ 2 ⟩ ⟩ . The symmetry of these two structures mandates that ⟨ ⟨ ψ ψ 1 | H | ψ ψ 1 ⟩ ⟩ = ⟨ ⟨ ψ ψ 2 | H | ψ ψ 2 ⟩ ⟩ = E .