D O C U M E N T 4 5 1 J A N U A R Y 1 9 2 7 4 4 5 way that the molecules in each quantum state can be treated as gas, and the whole thing as a mixture of such gases. Of essence is only that, according to the underly- ing hypothesis, from a certain density on, an increasing number of molecules lacking energy should result. Even if Pauli argues the opposite,[6] one may unhes- itatingly replace the summation by an integration, and essentially without ignoring anything, at that. This is because, as the total volume of the gas increases, the per- missible energy values for quanta pack more and more densely together. Another question is whether Fermi didn’t hit the right thing, after all, with his requirement that not more than one molecule may be inside a cell.[7] There are two opposing aspects to this question: light-quantum molecule analogy (1) Pauli’s dual-occupation exclusion.[8] (2) Both together cannot be fulfilled here. My way of calculating is based on (1) and violates (2) Fermi’s is based on (2) and violates (1) (because, despite Nernst, radi- ation has no zero-point energy[9] and anyway, because only thus does Planck’s law result). Only experience can decide between the two hypotheses, which, due to the non- existence of such an ideal gas, however, is very tricky. 451. Opinion on Michele Besso [Berlin, before 13 January 1927][1] Besso. He has an acute intellect, he does not like confrontation that is why he counters every “either-or”[2] with a problem, and that is how he became a scientific (and thus very impractical) person. He cannot offer anything when someone is dogmatically resistant but the first thing he does is to try to overcome this resistance and arouse an interest in the ques- tion and in research. As soon as this interest is present, he is an exceptional sound- ing board for it. He is wholly tuned to understanding the viewpoint of the other and to revealing the problematical points in it that is why he is brilliant in a discussion. In it he pur- sues the goal of bridging oppositions and disagreements. This and the ability to penetrate into the thoughts of others makes him a productive critic. His strength lies not in that he creates the material for a framework himself, but rather in that, similar to Socrates, he polishes it and cooperates in that way. (He always called himself a midwife.)[3]