Pauli writes about the "abyss" which separates observation and comprehension and on the miracle that, in spite of this, scientific cognition is still possible and on Heisenberg's and Weisszäcker's scientific attitude.

This letter is an addition to the letter of 15 April.

Pauli writes about two problems: The H-theorem and five and higher dimensional field theories.

Pauli advises Klein on improvements to his Bohr-Festschrift article. He reports on receipt of Landan's article. Pauli makes remarks on Soviet contacts with the West.

Pauli makes editorial remarks on Klein's article. He reports on his trip to Holland.

Pauli writes about thermodynamical irreversibility and quantum theory. He makes remarks about Pais' work and his W-space, about quantum field theory and about the analogy between the electromagnetic eigen-field of an electron and the gravitational eigen-field of a photon.

Pauli gives his views on mutations and selection. He makes remarks on Klein's work and Heisenberg's attempts at a unified field theory. Pauli makes plans for a relativity congress.

Pauli writes about Kramer's death and the "shadows" in the last years of his life.

Pauli writes about his essays on Kepler which will be finished shortly.