Pauli describes his latest work in quantum mechanic and compares it with Heisenberg's work. He discusses his results.

Pauli makes some objections to Thomas' derivation of the missing factor in magnetic interaction of the spinning electron. He is opposed to its publication.

Pauli describes the theoretical tasks if the spinning electron is correct. He criticizes Thomas' relativistic derivation, published in: Nature : 117 (1926), 514.

Pauli agrees with Weyl's incorporation of gravitation in Dirac's theory of the electron, and with his rejection of Fern-parallelisme. He writes about as yet unsolved difficulties of Dirac's theory and two-component theory. He writes about field quantization.

Pauli comments on Heisenberg's letter and his introduction of the square of fluctuation in zero approximation.

Pauli indicates a weakness in Dirac's theory.

Pauli replies to Heisenberg's letter of the 1st February.

Pauli writes about Uhlenbeck's appointment in Utrecht. Pauli is glad that Kronig has written to him, in spite of Pauli's remark regarding the spin problem (in Tübingen). Pauli makes some remarks about him and Uhlenbeck. He thinks that Kronig should go to America, in spite of his doubts. He makes remarks on Jordan's and de Broglie's paper on the neutrino.

Pauli welcome's Jauch's impending appointment in Princeton University and gives advice as to the negotiations about working conditions. Enough time for research is vital. He comments on the difficult paper by Dirac. He suggests a problem in the same area (application to "infra-red catastrophe"). He writes of his plans for a joint investigation with Kusaka about application of the strong-coupling formalism on a mixture of mesons of zero spin and spin 1 (Rosenfeld-Möller theory).

Pauli has received from Rosental a copy of Bohr's article for "Dialectica" and Bohr's letter. This article will be of great help to him to clarify the contents of other articles in the issue, particularly Bohr's definition of "phenomenon". It would be a great help for the general editorial comment on the whole issue, if Bohr could return to Pauli the proofs of Einstein's article and also drop him a line on his opinion about the remarks which Pauli made himself in his letter to Einstein (of which Bohr has a copy). Every criticism is welcome.