"The history of QED in the period from 1946 to 1949 has many similarities with the history of the developments of quantum mechanics from 1925 to 1927, when Schrödinger and Heisenberg had propounded two different approaches to quantum mechanics. The correspondence can be taken to be: Feynman is to Heisenberg what Tomonaga-Schwinger is to Schrödinger, with Dyson initially playing the role of Pauli, Schrödinger, and Eckart in proving the equivalence of the two approaches."