Pauli asks for details about Gürsey's formalism with a non-degenerate vacuum. He enumerates several problems which worry him, e.g. mirror states, classification of elementary particles, etc...

Pauli writes on the treatment of the eigenvalue problem. The only existing method is the Tamm-Dancoff approximation but Pauli does not believe in it. He will possibly work on the problem with Gürsey. He speaks of a principal difficulty of model which is analogous to that in the "neutrino-theory of light". In the spinor model Pi-mesons and photons are composed of real states and only formally existing mirror states which must be forbidden. There is a discussion of the difficulties resulting from this.