Despite the fact that the KS-DFT determinant inevitably describes the density matrices of reactants and transition states with different accuracy (i.e., the exact two-body density matrices d pqrs differ more or less from the single-determinant D pq D rs ), KS-DFT is able to obtain good results in reactivity through use of an exchange functional of the density E xc [ρ]. This statement also applies to the success of "density corrected" DFT (DC-DFT), in which the densities used in the KS-DFT energy expression (eq. 3) come from HF determinants (i.e., the functional has no input on the density, but only the energy calculation). This leads to the hypothesis that the ASIE found in CASSCF may come in large part from unequal contribution of the density cumulant between two geometries, d pqrs -D pq D rs . A multiconfigurational approach that avoids use of the density cumulant by means of an exchange-correlation functional may inherit much of the equal-footing properties of KS-DFT and prove more robust against ASIE.