Pauli makes some criticisms of some of Källén's results "not in order to criticize but in order to learn".

Pauli replies to Källén's letter of the 2 January 1957. He agrees to his interpretation of Heisenberg's ideas. He talks about Heisenberg's tendency to modify his assumptions if he is refuted.

Pauli talks on further calculations about dipole-ghosts. He asks about Eta-matrix.

Pauli replies to Weisskopf's letter of the 22nd December 1957. He writes about his scientific correspondence with Heisenberg, and his own suggestion for a extension of the Lee-model. He writes about the possibility of two sorts of neutrinos. He writes about lepton charge and its conservation and about parity violation.

Pauli talks about analysis of the defects of Heisenberg's approach and of some errors in his conclusions.

Pauli replies to Källén's letter of the 22 and the 28 January 1957. Pauli declares himself uninterested at the moment in indefinite metric. He talks about parity and the two-component theory of the neutrino. He writes on the possible existence of symmetries and the theorem of "strong reflection" and its consequences, on the possible influence of a yet unknown field and arguments from experience against this hypothesis and on connections of parity-violation with other not yet explained facts. He wonders why strong interactions have left-right symmetry. The present formulation of the theory allows for too many posibilities. Posssibly interactions create space, time and their symmetries.

Pauli accepts the invitation to the Nuclear Structure Conference at the Weizmann Institute.

Pauli writes on the question of the conservation of lepton charge in connection with Majorana's theory.