(2.1.26) Görling : While the electron density certainly is a key quantity in DFT, I feel that there is a too strong focus on it -in particular, on the idea of getting the total energy or other information directly from the density. While this is the idea behind certain flavours of orbital-free DFT, it is not the idea behind the most commonly used DFT approaches, which are the Kohn-Sham or generalized Kohn-Sham methods. For these methods, a quite different view on DFT can be taken: To consider the electron density as the quantity that enables one to associate the real electronic system with a model system that has the same groundstate density, which makes it possible to describe the ground-state energy and other properties of the real system via the model system, i.e., via its orbitals and eigenvalues. From the Kohn-Sham orbitals, traditionally, only the 'noninteracting' kinetic energy is calculated exactly, while the exchange-correlation energy is approximated by an explicit functional of the density.