Pauli makes two additions to the last letter. He thinks that Jordan's model with gravitational constant does not differ in principle from models with constant k.

Pauli makes more remarks about biology. Science can deal only with reproducible events. Historically unique events lie outside the domain of science although they are part of nature.

Pauli replies to a number of printed papers from Jordan: on Jordan's 5-dimensional theory, on his theory of formation of stars, and about quoting Pauli in publications on parapsychology.

Pauli writes about Jordan's article in the Bohrfestchrift which deals with the role of chance in biology. Pauli criticizes the use of the concept of chance in biology and evolution in particular.

Pauli writes on technicalities about Pauli's impending visit to Hamburg.

Pauli agrees with Källén about an error in Thirring's paper. The question now is whether Hurst's paper is correct.

Pauli talks about questions in connection with the preparation of a lecture on problems of quantum electrodynamics: 1) about Lee's non-relativistic models for renormalization, 2) about longitudinal photons, 3) about a paper by Green published in: Physical Review 95, 548 - 1954.

Pauli thanks Källén for his reply. He objects to his views on the gauge-invariance. He writes on the danger for a theoretical physicist to stick to one special formalism. This is also Källén's mistake in his formulation of the Lee-model.

Pauli replies to Källen's letter and continues the topics in Pauli's last letter. The coupling-free case has to be eliminated from Lee's model because it does not exist in nature.