Pauli writes about the question of finiteness or infinity of charge density in the hole theory.

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 writes of his discussion with Weisskopf about Heisenberg's letter to the latter. The result is electrical polarizability of vacuum and self energy are analogous phenomena. The perturbation formalism of substraction-physics can lead to the removal of these phenomena.

Pauli has come to the conclusion that the results of his last letter were wrong, self-energy remains infinite. But it is different with the self-energy of charged particles.

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

Pauli comments in detail on the paper by Einstein-Podolski-Rosen and suggest that Heisenberg should write a reply. He analyzes the problem of composition and separation of systems in quantum mechanics. He is against Laue's and Einstein's idea that quantum mechanic is correct but incomplete. He comments on Wick's paper on the magnetic moment of the proton.

Pauli gives a detailed exposition of his calculation of the energy eigenvalues in Fermi's theory, and adds some hypothetical conclusions to this.

Pauli writes about an unpublished lecture by V Neumann where the mathematics of the density matrix is developed.

Pauli makes some remarks on Heisenberg's letter of the 7th November, based on his own former calculations.