Pauli replies to Pais' letter about W-space. He talks about the connection of Pais' theory with those of Kaluza and Klein. He writes about the geometrization of meson-nucleon forces.

Pauli supports Pais' application to come to Princeton. He is favourably impressed by Pais' work.

Pauli writes about a paper by Villars and himself for the Einstein issue of the Rev. Mod. Phys. which will be sent off in a week. He asks if a certain result is already known. He writes about self-energy and "self-stress" of the electron. He also mentions Kramer's state of health.

Pauli writes about Kramer's death (24 Apr) and their friendship. He writes of his forthcoming visit to Copenhagen (meson conference).

Recommandation of Princeton.

Pauli gives a preliminary answer to Pais' manuscript and letter. He makes some critical comments on Pais' treatment of Born's theory of the electromagnetic field. He makes corrections to his 1943 article on Dirac's theory of negative photons.

Pauli emphasizes the importance of Pais' result for the current density of zero-spin particles. But he expresses concern about the substraction formalism. He writes about his contribution to the Einstein-Festschrift.

Pauli talks about the sign of vacuum polarization. He says that the vacuum polarization charged auxiliary particles must be introduced (positive and negative, zero spin).

Pauli replies to Pais' question about the transformation of Hamiltonians.

Pauli criticises Jung's theory of the closed circle, but in spite of this he thinks that the concept of the Collective Unconscious is correct and plausible. He gives a detailed discussion of this concept and modifications. He makes parallels between micro-physics and psychology of the unconscious which deal with an invisible reality. He writes about Bohr's political activity and the reaction to it.