Pauli is glad about Heisenberg's impending visit. He writes a few words about the next stage of the discussion, especially the eigenvalue problem for rest masses.

Pauli says that he reached similar conclusions to Heisenberg.

Letter amplifying his cable from the boat to the USA, urging Heisenberg not to publish now and not to send anything off before giving Pauli an opportunity to express his view. He wants Heisenberg's clear reply on the degeneration of the vacuum, mirror states, the metric in Hilbert space and the eigenvalue problem. He gives more details about the last point. He writes about reactions of colleagues (also Bohr) in New York to their ideas. The scepticism of Yang and Lee and of Heisenberg's pupils, has made Pauli feel that publication should be deferred.

Pauli replies to Heisenberg's letter of 10 February to tell him that in Berkeley he has the opportunity to discuss their work with many people. He has more questions about the mirror-world (mirror nucleons and mirror difficulties of the spinor model and some problems of mathematical formalism.

Pauli gives more suggestions for the preparation of the publication. The connection of vacuum degeneration and strange particles must be emphasized. He has other suggestions for a clearer representation of their results.

Pauli replies to Heisenberg's letter of 25 and 27 January. He writes about particles with rest mass zero and leptons with rest mass different from zero which have no strong interaction. He talks about the radio publicity given to heisenberg.

Pauli thinks it's important to explain the lack of strong interaction in leptons. He talks on the necessity of giving explanations on some points of the table summarizing the properties of the elementary particles.

Pauli writes of a paper by Dürr which contains answers to all questions left open in Heisenberg's letter. He is going to study this paper.

Pauli replies to Heisenberg's letter of 15 March. He emphasizes the discrepancy of their respective views on symmetry diminuation, spatial boundary conditions and rest mass zero . He specifies their differences of opinion. He writes about the logical possibility that electromagnetism and photons cannot be explained by a spinor model.

Pauli emphasizes that in spite of the difficulties his attitude to the theory of holes is not negative. He gives some comments on the magnetic moment of nuclei and of the neutron. If the laws of nature are completely symmetrical with regard to positive and negative electricity, a negative proton should also exist and the free neutron should exist in two states, if its magnetic moment is different from zero.