Pauli asks questions about a paper by Nishijima.

Pauli suggests a note correcting the results of Nishijima. He questions whether Heisenberg's description of physical scattering processes in the Lee model comes to grief through discrete states of negative norm or of complex energy He also asks whether "Heisenberg-models" can be constructed for which the unitarity of the S-matrix is preserved in an indefinite metric of the field-operators?

About Pauli's contribution to a conference in Rehovot (Israel).

Pauli congratulates Thellung on his engagement and professorship. He expresses his satisfaction about the choice of his new research subject : heat conductivity at low temperatures. He makes a short report on his Mediterranean trip.

Pauli discusses the communication problems he has with Springer.

Pauli agrees to Bergmann's comments on Misner's argument concerning the vanishing of the Hamilton function.

Pauli rejects Fierz's criticism of his physical interpretation of complex energy values for an indefinite metric. To prove his case, he treats the interaction with the help of perturbation theory.

Pauli explains to Fierz why he believes that the elimination of non-physical states in the quantized field theory is only possible if the space-time description is dropped, i.e. in a pure S-matrix theory.

Pauli replies to Heisenberg's letter of the 9 December. He writes on the question of "real" and "complex" ghosts.