The same observation, coupled with the fact that the quality of the response of the density depends on the quality of the density, also enabled the extension of Kohn-Sham DFT to electronic structures that have multi-configurational character and, therefore, are not well described by the single determinant. Although with exact Kohn-Sham DFT, we should be able to treat any type of electronic structure, current DFAs implicitly rely on the expectation that a single Slater determinant provides a good zero-order representation of the wave function; consequently, most Kohn-Sham DFAs fail when the electronic structure is multi-configurational.