D O C U M E N T 1 0 1 N O V E M B E R 1 9 2 5 1 2 1 This dissymmetry assumption by Planck seems to me the least secure, though. It is not yet entirely clear to me whether anything in your reflections would change if they were abandoned. Dynamic degeneracy is surely connected with the occur- rence of symmetries (such as, e.g., with the diatomic molecule out of identical atoms). It isn’t clear to me yet whether the statistical weight, which is diminished by the symmetry, is brought right back to N! by this degeneracy (in which case your derivation would remain untouched).— In any event, I shall consider this matter completely as best I can and am most extraordinarily grateful to you for the new light you have kindled inside me.— Currently I am exchanging letters with Landé about his quantum interferences (Z[eitschrift] f[ür] Phys[ik], 33, p. 571).[7] The idea seems to me to be very inter- esting but not properly thought through. How is Planck’s (instead of Wien’s) radi- ation law supposed to result if the individual quanta are distributed throughout the cells, as if they did the interference independently and only retroactively, inside their cells, but only such that the mean energy of a larger number of cells, each con- taining j quanta (of the same kind), is not altered by the interference? Landé’s response is: Well, it is not the energy that is altered, but the entropy it is supposed to be judged from the resulting content of the individual cells. Very well. But the entropy here only plays the role of a measure of probability. Consequently, if the probability is supposed to be judged from the resulting cell content, well, then the quanta will not be distributed quasi-independently throughout the cells and the whole advantage of L’s conceptual approach, which, of course, is supposed to be an explanation for the strange preference of quanta to “squat together,”[8] seems to me to be lost.— Two other objections are aimed at the faulty application of the formulas (which only apply with large numbers) to very small numbers, and are less meaningful in principle than the first objection, if it is valid.— A few days ago I read with the greatest interest the inspired theses by Louis de Broglie, which I was finally able to get hold of [9] thereby, §8 of your second de- generacy article first became fully clear to me as well.[10] — De Broglie’s interpre- tation of the quantum rules appears to me to have connections with my note Z[ei- tschrift] f[ür] Phys[ik], 12, 13, 1922, where a strange property of Weyl’s “gauge factor” is shown along each quasi-period.[11] The calculational matter is the same, as far as I can see, only that mine is presented much more complicatedly, less elegantly, and actually not generally. It goes without saying that De Broglie’s consideration within the framework of his grand theory is of incomparably higher value than my individual finding, which I initially did not know what to do with. Again many thanks to you, dear Professor, for your two kind letters, which are so valuable to me, and best regards, yours sincerely, Schrödinger e –³ϕidxi