Pauli proves that Heisenberg's theory given in his letter of the 6 November 1933 is identical with a former theory developed by Pauli and Heisenberg.

Pauli agrees with Heisenberg's pessimism regarding infinite energies, but he thinks one should try to separate the problem of self-energy from that of the hole theory.

Pauli does not believe that the theory of holes can be improved without essentially new ideas.

Pauli writes of Weisskopf's and his own result that the material energy of photons becomes infinite in their theory. He remarks about "substraction physics": the fact that polarizability of the vacuum and self-energy of material particles are both becoming infinite must have a common root. The real progress of the theories will be found in the amalgamation of electromagnetic field and matter field.

Pauli believes that the introduction of singulary density matrices is not the physically correct way to a solution.

Pauli writes on some afterthoughts about Heisenberg's letter.

Pauli writes that his view that Delta-type interaction between more than two neutrinos must lead to infinities was influenced by a paper by Thomas (Phys. Rev. 47,903). This does not affect Pauli's and Heisenberg's case.

Pauli takes back what he said in the last postcard and confirms Heisenberg's calculations.

Pauli comments on a paper by Uhlenck-Konopinski and by Anderson-Neddermeyer on particles with masses between that of electron and proton, which opens completely new vistas.

Pauli congratulates Heisenberg on the birth of his child. He makes a remark on the cut-off frequency of long waves and about Yukawa's theory of nuclear forces.