Pauli replies to questions from Heisenberg in his letter of 4 November 1934. The self-energy of the electron in Pauli's theory becomes logarithmically infinite . This theory can only be developed with Bose-statistics. He writes about the Lagrange function of the scattering of light by light and about the magnetic moment of the neutron and the symmetry of the laws of nature with regard to the sign of the charge. He talks about the magnetic moment of the proton and the deuteron.

Pauli makes a comparison of Klein's theory with his relevant lecture given in Paris.

Pauli agrees with Heisenberg about V Neumann's paper. He also believes in the significance of a universal length.

The letter contains more remarks on the same model.

Pauli aknowledges receipt of Kemmer's manuscript. He asks him to look into the latest American papers on nuclear forces.

Pauli agrees with Heisenberg's suggestion (letter of 2nd February) for the modification of his theory, and adds some remarks on this.

Pauli apologizes for a mistaken criticism by Fierz on a theory by Uhlenbeck.

Pauli comments on a paper by Heisenberg about nuclear forces and its relation to the Yukawa-theory.

Pauli makes two remarks concerning Heisenberg's letter of 5 April about nuclear forces.

Pauli agrees with Heisenberg's letter of the 23 May which clarifies the question of decidability between various laws of force in proton-neutron scattering.