Peierls offers a proof of the Jacobi identity, and reports on progress in his work on non-local field theories,which includes finding a method which leads to reasonable solutions of the action principle.

Peierls refers to the Møller-Kristensen theory. He says that the difficulties with their theory may arise from discontinuities in the form factor.

Dyson writes about Baranger's calculation of the relativistic correction to thesecond order lamb-shift. He adds to the letter his ideas about the renormalization programm.

Peierls replies to two letters by Pauli. He comments Pauli's calculations as regards the non-local field theory, and on his view about the use of form-factors which may destroy the gauge invariance.