Pauli encloses a letter to Springer. He talks about a new paper by Schwinger on elementary particles. He writes on the logical connection of Källén's recent results to an example given by Jost last spring. He also talks about Thirring's model.

Pauli replies to Heisenberg's letter of the 30 October, on $\gamma$-invariance and conservation of electric charge: which group corresponds to this? He talks about mirror-invariance in isotopic spin space.

Pauli writes about his interest in Touschek's remark at Padova and Venice about the derivation of C- and P-symmetry from special properties.

Pauli makes critical comments on Fierz's last letter and his calculations. He writes on speculations about C-, P-, T-invariance. Possibly it is not the strength of the interaction but primarily its form which determines C-, P-, T-invariance.

Pauli makes remarks on Misner's work: the Hamiltonian density cannot vanish, neither classically nor with quantization.

Pauli is against Heisenberg's approach to quantum electrodynamics. It is impossible to work only with energy-momentum values and the S-matrix and to disregard space and time. He talks about some clarifications on his own last letter but one. He writes on the separation of purely mathematical quantities from physically significant ones.

Pauli replies to Lüders' letters of 8 Dec and 13 Dec about elementary particle theory.

Pauli replies to Källén's letter of the 13 December 1957. Pauli agrees with him that the indefinite metric is the correct way. He talks about the macroscopic space-time description with complex roots and the Bisection of zero-states in parts corresponding to the upper and lower half-plane which must be connected with the difference between observed object and observing subject. By this bisection symmetric violations are introduced in a most natural way. He writes on his discussion with Heisenberg and on complex ghosts in weak interactions.

Pauli talks about the logical possibility of getting particles with mass different of zero in a world with $\gamma_{s}$-invariance and hints at another "unconventional" solution of the problem.

This is the continuation of the letter of the 16 January 1958. Pauli gives a new idea of indefinite metric.