 PMI starts with the dynamical state of the whole universe with respect to itself, which it is assumed to be a pure state \(\varrho_{U}^{U} = \ket{\psi} \bra{\psi}\), evolving unitarily according to the Schrödinger equation. For any system \(S\) contained in the universe, its value state with respect to itself \(\varrho_{S}^{S}\) is postulated to be one of the projectors of the spectral resolution of \(\varrho_{U}^{S} = \mathrm{Tr}_{(U\setminus S)} \varrho_{U}^{U} = \mathrm{Tr}_{(U\setminus S)} \ket{\psi} \bra{\psi}\). In particular, if there is no degeneracy among the eigenvalues of \(\varrho_{U}^{S}\), \(\varrho_{S}^{S}\) is the one-dimensional projector \(\ket{\psi_{S}} \bra{\psi_{S}}\).