Pauli replies to Lüders' letter of 26 April. He talks about problems of coordinate-mirroring, of particle-antiparticle conjugation and of invariance of the equation with regard to the continuous Lorentz group.

Pauli replies to a letter of the 25 July 1954. He explains his critical attitude to ontology but he conceeds that ontology reflects an intrinsic need of man to overcome the tension between the "Internal" and the "External".

Pauli talks about his work on the Lee model and about Thirring's progress with the divergence of the Dyson series.

Pauli talks about the excited state of a V-particle. The renormalization procedure seems artificial after the discovery that there exists more than one eigenvalue W$_{o}.

Pauli writes about further thoughts on biological questions. He writes about a book by Rensch on evolution, which has impressed him very much. He writes about psycho-physics parallelism, and about a book by Soal and Bateman on modern experiments in telepathy.

Pauli has some more considerations about the Lee model. He talks about some mathematical developments and their possible use for more complex systems with renormalization mathematics, especially quantum electrodynamics.