Heisenberg agrees with Pauli that one cannot make the S-matrix alone a starting point of a quantized field theory. There is discussion of other possible presuppositions.

Pauli thanks him for his letter of 26 Dec. He would like to hear more from him about Heisenberg's S-function. He writes about the translation of Pauli's handbook article into Japanese.

Pauli writes about the failure to decide mathematically wether the renormalized and Lorentz-invariant quantization of electrodynamics constitutes a consistant theory. He writes about his visits to Hamburg and Copenhagen and to the relativity conference in Berne.

Pauli asks Thellung to send the English edition of his book on Kepler to Rabi.

Pauli writes about the destruction of symmetry between the "internal" and "external" in our age. Science systematically excludes the observer from its results. Since Kepler, there has been no mystic in science. He also comments on a talk with Panofsky on the parallel between the myths of paradise, Eve, and the Pandora's box.

Pauli makes some comments on Källén's exposition on "Retarded functions of two variables".