Pauli writes about his renouncing the partnership with Heisenberg. He thinks there are mistakes in Heisenberg's integration of his equation. Futher, if one attempts to loosen either the causality or the unitarity of the metric, this leads to disastrous results in relativistic theories. His impression is that one has to wait for new physical ideas, because mathematical virtuosity alone cannot lead to the discovery of new laws of nature.

Pauli replies to Heisenberg's letter of 13 April. He criticizes his pressing for a premature publication of the work. He is now convinced that some of the field equations have nothing to do with the real nature of the elementary particles. Possibly, at the present stage of quantized field-theories and on the level of special relativity, a theory of elementary particles is impossible without ad hoc assumptions.

Pauli comments on Schafroth's preprint. He hopes that with Bogoljubow's and Wentzel's work one can arrive at a possible model for supraconductivity.

Heisenberg writes about the progress of his work, together with Dürr, Schliederand Yamasaki. They are going to describe the theory for nucleons and Pi-mesons. Heisenberg gives an explanation of their ideas.