(3.8.10) Helgaker : I sometimes wonder whether we as a community would know less about the role of dispersion in chemistry and physics if DFT had not struggled to describe it. By being able to turn on and off dispersion as described for example by we have observed the effects of dispersion in a very transparent manner -this was for me, at least, an eye-opener. In general, DFT forces us to discuss the real world in a different manner than wave-function theory.