In Table , we also list the results on the agreement of the electron density of noninteracting reference system with the density of the physical system as defined by the linear response. (2.2.18) Trickey : The pervasive emphasis on the KS orbitals to this point in the discussion is striking and, from the perspective of my interest in orbital-free DFT, a bit overbalanced. From that perspective, the KS orbitals and eigenvalues are not the crucial insight provided by the Kohn-Sham decomposition -that crucial insight is the existence (assuming v-representable densities) of a noninteracting system with the same density as the many-body system. With that assumption, existence is provable by application of Levy 6 -Lieb for the ground-state and Runge-Gross (as updated by Ruggenthaler, et al. ) for the time-dependent case and Mermin for the temperature-dependent case. The orbitals (and eigenvalues) are a valuable, exploitable by-product.