When I meet a difficult problem, I begin to go around it, approaching it again and again from different directions. If I persistently continue these approaches, it can happen that no problem remains. (RolfNevanlinna, in a private discussion.) In 1976, after a mainly administrative period of some 15 years, I spent a couple of months at CERN, working in the Pauli Collection. When I found the Pauli-Fierz correspondence, I had the intuitive feeling that...