Pauli thanks Gustafson for having sent him Källén, who has great talent.

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 sends the copy of a letter from Pauli to Paul T Matthews (dyson_0065-1). The letter shows that Pauli regardsthe electrodynamics of charged scalar mesons as solved.

Heisenberg sends Pauli the manuscript of a paper on elementary particles for criticism. The starting point is not quantum electrodynamics but a kind of general philosophy of elementary particles. He gives some comments on his manuscript. The fact that protons do not decay into positrons and photons must be based on a conservation law for nucleons.

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.