Heisenberg asks about the program of the forthcoming conference in Zürich.

Heisenberg explains his ideas about the "Vertauschungsrelationen" (interchange relations) in his paper. The real problem arises after the introduction of an interaction. This belongs to the general question: which invariance conditions are fullfilled by the interaction energy? He is not as pessimistic as Pauli, the whole question boils down to the problem of finding suitable expressions for interaction out of combinations of wavefunctions which obey regular interchange relations. One has to begin by forming models for unitary theories which afterwards will split up in theories for single particles. The postulate of "hermiticity" is connected with the conservation law for nucleons.

Heisenberg thanks Pauli for the invitation to the symposium in Zurich.

Heisenberg must cancel his participation in the philosophical congress in Zurich because of his journey to the U.S.A.

Heisenberg comments on Pauli's calculations on the Lee model. He writes about his own work, especially on Bosons of zero mass in his model.

Heisenberg writes on the application of Pauli's ideas to quantum electrodynamics and on the avoidance of ghosts.

Heisenberg talks about some relations between Lee's theory and his.

Heisenberg writes on the difficulties of the renormalization procedure.

Heisenberg writes a summary of his theory: axiomatics, properties of elementary particles, ghosts.

Heisenberg writes on an invariance property of the ghost solutions.