Bohr agrees with almost everything in Pauli's last letter. He reports on a long discussion of Heisenberg's theory and its relation to the earlier quantum theory and on the missing aspects and the future of Heisenberg's theory. His letter has given rise to many changes in Bohr's paper of which he encloses a proof published in: Nature : 116 (1945), 845 and in: Naturwissenschaften : 14 (1926), pp.1.

Bohr has made some arrangements for a room for Pauli from April 4.

In April, Darwin, Kramers, Goudsmit and Waller are expected to come to Copenhagen. Bohr asks Pauli if he could also come.

Bohr has sent his manuscript to Naturwissenschaften and asked Berliner to send proofs to Pauli. Most of it is well known to Pauli, but some additions are new. He asks Pauli to send him proofs with critical remarks.

Bohr's thanks Pauli for his enjoyable and interesting letters. The three pages of the letter contains many scientifical questions.

Bohr thanks Pauli for his letters with the quick and thoroughgoing answer to his small heart-outpouring. He and Rosenfeld studied Pauli's letters very carefully and agree of course with most of the contents. Bohr thinks that Pauli underestimates the consequence in the correspondence-attack on the atomic problems based on the low value of the fine structure constant.

Pauli's last letter was in every respect a cause of great pleasure to Bohr. First of all Bohr and his wife sends Pauli their heartiest congratulations on his approaching wedding and they look forward to having Pauli and his wife on a small visit in their home. The week after Easter would be very suitable, and Bohr hopes that they will feel comfortable in Carlsberg in spite of the columns. Both Rosenfeld and Klein, who is in Copenhagen on a visit, as well as Bohr, were very interested in Pauli's remarks. Bohr will take Pauli's proposals into consideration when the proofs arrive. The unknown author of the first appendix writes that he agrees very much with the contents of Bohr's manuscript and his letters to Pauli. By contrast his view about the problem of the infinite self-energy is somewhat different from what Bohr writes on this subject.

Bohr was glad to receive Pauli's article which gives an excellent account of Einstein's pioneering work in quantum theory. Bohr does not know what to answer to Pauli's questions concerning some changes Bohr should make in his paper. The detailed account of the discussions which he had first planned turns out to be much too long for the occasion. Therefore, he is trying to confine himself to the general epistemological aspects of the attitude taken in the discussions, and he has started on a much shorter article which he hopes to have ready very soon. In a few days Bohr will write to Pauli again and tell him how things stand so that it can be decided how to make the best out of it all.

Professor Bohr was very glad to have Pauli's letter of the 26th March. Since Bohr wrote last he had a visit from Delbrück, who, as Pauli knows, will stay in Göttingen this summer. This visit gave an opportunity for many instructive and interesting discussions with Danish biochemists and biologists. Bohr feels still more convinced that the general considerations about organic development, about which Bohr wrote to Pauli in January, hit a quite important point. He hopes to be able to give a more clear account of such questions in a lecture "On the unity of knowledge" at "the bicentennial celebrations" at the Columbia University in Autumn.

Bohr's reply to Pauli's letter of the 15th February. He explains his use of the phrase "detached observer" and writes on the necessity to clarify the terminology.