Pauli letter collection: letter to Wolfgang Pauli

Heisenberg explains his ideas about the "Vertauschungsrelationen" (interchange relations) in his paper. The real problem arises after the introduction of an interaction. This belongs to the general question: which invariance conditions are fullfilled by the interaction energy? He is not as pessimistic as Pauli, the whole question boils down to the problem of finding suitable expressions for interaction out of combinations of wavefunctions which obey regular interchange relations. One has to begin by forming models for unitary theories which afterwards will split up in theories for single particles. The postulate of "hermiticity" is connected with the conservation law for nucleons.