(3.2.17) Gidopoulos : In our group, we share the view that self-interactions are behind the errors of Kohn-Sham orbital energies, an opinion advocated strongly also by Rod As Baerends explains, the effects of self-interaction are not evident in the DFA total energy and the error in the Kohn-Sham orbital energies is about an order of magnitude greater than the error in the total energy. So why blame self-interaction for the Kohn-Sham orbital error? Our reasoning for arguing that the errors in the Kohn-Sham orbital energies are due to self-interaction, when even the definition of self-interaction in the total energy is unclear, is simple.