Fierz writes on the problem of leptonic charge.

Fierz writes on the symbolic significance of birds and on two physical description.

Fierz writes on the significance of the "causal function Dc" in quantum electrodynamics.

Fierz gives some developments about the problem of space, and the ideas of Newton and the Cambridge "Platonists" of his time. He makes some remarks on Pauli's suggestions about the word "automorphism" on generalization of the quaternity (+,-) and (p, q).

Fierz responds to Pauli's aversion to the half-integral rotation group by deriving its properties. He gives in attachment Pauli's calculations. Fierz also defends Bohm's ideas against Pauli's criticism.

Fierz replies to a letter written by Pauli, on gravitational waves and on form factors.

Fierz defends his position that entropy is the "measure of information" obtained by an observer. He examines information obtained in classical theory from observation of changing macrostate; in quantum theory from observation of microstate that is then generalized to a macrostate. He claims entropy exists only with observation.

A sketch of a statistical theory of a dust particle.

Fierz comments on Jordan's attempt at deriving the gravitational equations from a variation-principle. He writes on speculations on the possibility of explaining life scientifically.

Fierz makes some additions to his letter of the 15th May 1951.