Pauli talks about his final views on the formulation avoiding infinities. He is against the tendency of Källén to use cut-off methods. He has a suggestion for a joint publication "on the mathematical structure of Lee's example in renormalizable field theory". He writes a synopsis of the suggested paper.

Pauli writes of Landau's paper "The quantum theory of fields" for the Bohr-Festschrift and comments on it. He says more about the Thirring-model and about Heisenberg's paper on the non-linear spinor-equation.

Pauli writes about Thirring's reply to Pauli's criticism. He talks about an error in Pauli's last letter concerning quantum electrodynamics. He writes about a discussion with Thirring at the Bern-conference about indefinite metric.

Pauli talks about publications in Russia on quantum electrodynamics.

Pauli makes some comments on Källén's exposition on "Retarded functions of two variables".

Pauli replies to Källén's letter of the 3 October 1956. He writes about a proof by Symanzik concerning dispersion relations.

Pauli talks about a letter he received from Heisenberg about his recent considerations regarding the Lee model. The problem is where does the unitarity of the S-matrix fail in the case of indefinite metric.

Pauli makes some criticisms of some of Källén's results "not in order to criticize but in order to learn".

Pauli replies to Källén's letter of the 2 January 1957. He agrees to his interpretation of Heisenberg's ideas. He talks about Heisenberg's tendency to modify his assumptions if he is refuted.

Pauli replies to Källén's letter of the 22 and the 28 January 1957. Pauli declares himself uninterested at the moment in indefinite metric. He talks about parity and the two-component theory of the neutrino. He writes on the possible existence of symmetries and the theorem of "strong reflection" and its consequences, on the possible influence of a yet unknown field and arguments from experience against this hypothesis and on connections of parity-violation with other not yet explained facts. He wonders why strong interactions have left-right symmetry. The present formulation of the theory allows for too many posibilities. Posssibly interactions create space, time and their symmetries.