Heisenberg writes about the qualification of some of his results in the last letter. The theory still seems promising.

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.

Heisenberg doubts about the usefulness of the Yukawa-potential for nuclear physics. He talks about the relative abundance of light and heavy particles in explosions.

Heisenberg talks about the classical electron-radius as an upper limit of the universal length. He does not believe in Pauli's remark that the potential between proton and neutron at larger distances can be found from mass-defect measurements. In the "wave-like" region one cannot from the potential at large distances and effects resulting from the failure of quantum mechanics for p~h/ro.

Pauli talks about the question of Beta-spectra. The literature gives ample evidence against Heisenberg's hypothesis.

Pauli writes on philosophical remarks on the essence of the human spirit, on Jung's archetypes and feeling of evidence and on the significance of irrational factors in life.

Pauli asks Dirac to help a young jewish cousin of his who was forced to leave Austria for racial reaons and is now in danger to be expelled from Switzerland. He writes about his recent investigations with Fierz on particles with an arbitrary spin. He asks if they could be published in the Proc. Roy. Soc. He makes some remarks on Dirac's paper on the theory of the electron.