This is a supplement to the letter of the 26th May 1957. Pauli comments on a theoretical paper by Preston (Birmingham) which fits well with Pauli's critical attitude towards the two-component theory. He writes about Preston's proposal to give up the conservation of leptons. Pauli thinks that T-invariance seems still to be possible.

Pauli makes a few more remarks on Heisenberg's manuscript.

Pauli replies to Heisenberg's letter of 17 June, on pedagogical questions and on questions of principle.

Pauli talks about a manuscript sent by Heisenberg and a question whether unitarity of S-matrix, commutativity of field-operators and regularity of commutators on the light-cone can be fulfilled in the case of abandoning a positive-definite metric. He writes about Wightman's axioms and their inapplicability to physics.

Pauli writes about parity-violation. Includes an appendix about two-component theory.

Pauli talks about some remarks by Källén on Heisenberg's manuscript.