Heisenberg sends Pauli the manuscript of a paper on elementary particles for criticism. The starting point is not quantum electrodynamics but a kind of general philosophy of elementary particles. He gives some comments on his manuscript. The fact that protons do not decay into positrons and photons must be based on a conservation law for nucleons.

Heisenberg states his view on the question of the field theory and emphasizes the significance of the Möller-Kristensen theory as a well analyzed example for further theories of this type.

Heisenberg replies to Pauli's letter. He agrees with him as to the insufficiency of the concept of causality for the explanation of evolution. He also expresses doubts as to whether Pauli's concept of "sinnoller Zufall" can lead to a better biological evolution. The second part of the letter deals with Heisenberg's ideas about a quantized field theory.

Heisenberg writes in clarification of an error in his calculation concerning the operator xa (xx').

Heisenberg replies to Pauli's letter and detailed discussion of Källén's arguments concerning Heisenberg's quantum field theory.

Heisenberg writes about two additions to his last letter, on a certain spinor and on the conditions for the finiteness of certain operators.

Heisenberg talks about calculations to prove the vanishing of the transitions to dipole ghost states by a limiting process, starting from the Lee model.

Heisenberg replies to critical comments by Pauli.

Heisenberg asks Pauli's opinion about the model by Cooper and Deser, and about the possibility of formulating a renormalized theory which contains only finite operators.

Heisenberg writes on two limits, defined by a maximal- and a minimal-condition, within which a theory of elementary particles is possible.