Pauli comments on Fierz's difficulties in treating the problem of the spin-electron in a magnetic field. He makes some remarks concerning Kepler's astrological ideas.

Pauli attached to this letter a copy of a letter he wrote to Einstein, in which Pauli formulates his view on the physical reality and its description by quantum mechanics. Also attached is Einstein's answer to Pauli's letter (copy of the letter Einstein_0010r).

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.

Pauli writes on the concept of individuality in quantum physics and in psychology, on the identity of perception and intuition in the unconscious, and its connection with the concept of time.

In this letter Pauli raises the question whether Gibb's variation of thermodynamical functions preceeded Planck's work or not.

Pauli asks Fierz about Leibniz's principle of the identity of indiscernibles, which is mentioned by Weyl in connection with the exclusion principle.

Pauli writes on his own relation to physics and psychology as against Jung's, on the connection between synchronicity, statistical causality and deterministic causality and about the scientific thought as a special case of a coincidence of psychological expectation and external physical events.

Pauli writes to Fierz on a paper written by Yukawa, on a suggestion made by Fierz in this connection, on the present difficulties of quantized field theories and on his discussion with Panofsky in Princeton about Kepler and Fludd.

Pauli makes some remarks on a paper written by Heisenberg.

Pauli replies to a letter written by Fierz. He makes further remarks on Neoplatonists, on the Renaissance metaphysicists and on automorphism.