Pauli letter collection: letter to Gunnar Källén

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.