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.

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...