D O C U M E N T 1 7 5 J A N U A R Y 1 9 2 6 1 9 3 Meanwhile, Planck has thrown a new thought into the entropy debate, in the Zeitschr[ift] f[ür] Phys[ik], which seems to me to be very welcome, although it is more formal in character.[2] It is, of course, simply the old Gibbs lgV (V = phase volume) translated into quantum mechanics, which Planck now defines as entropy.[3] One is thus liberated from the unease caused by the indeterminacy of the energy interval for all the other definitions. Obviously, it is precisely this indeter- minacy, and the fact that it yields nothing, which is the interesting thing about the statistical concept of entropy (which Lorentz once called “the insensibility of ther- modynamic functions”).[4] I do find the claim that henceforth one would become “independent of the arbi- trariness that is always connected with establishing equally probable states”[5] a lit- tle sophistic. For one is compelled to count certain energy values multiple times (§4).[6] Planck’s account leads one to believe that, as soon as the quantum states are known only dynamically, one could also see at first glance what multiple each and every energy value must be counted by. But that is precisely the often so ticklish problem of determining weights.[7] — [I do not mean the worn out N!-problem, but the real determination of weighting and its ambiguity, e.g., in the five Reiche curves for the rotational heat!] Sincere and kind regards, dear professor, from yours truly, E. Schrödinger 175. To Leo Kohn [Berlin,] 22 January 1926 Dear Mr. Kohn, I am pleased that Weizmann has endorsed our approach.[1] I spoke in Paris.[2] Spineless fellows who cannot do anything without ¢renowned² animating Goyim.[3] But perhaps the people will gradually become more upstanding if they become a bit more Jewish-like with your help. I read the young man’s paper unfortunately, it is neither clear nor original. From this paper I cannot discern any talent, but do not wish to assert anything further.[4] Eddington was right.[5] At the inauguration in Paris, no representatives at all were there, so I had no opportunity to advocate on behalf of Jerusalem at the celebration.[6] Tell Mr. Weizmann that I cannot go to Stockholm.[7] Generally speaking, I must completely abstain from such things if I am to retain any influence that can serve our cause over the long haul. Still nothing from Magnes.[8] I presented my opinion to the Parisian Jews without inhibition. I also encouraged them to complain so that we—can downsize our Board of Gover- nors, as the large number of members is functionally untenable.[9]