1 2 8 D O C U M E N T 1 0 7 N O V E M B E R 1 9 2 5 where is the Maxwellian energy tensor. For it would be logically possible for “matter” to be described by a formally different kind of field than by a six-vector, without the gravitation term therefore having to be different. This lack of internal completeness bothers me very much. However, after many futile attempts, I don’t believe anymore that it can be overcome in the foreseeable future I rather think that the Weyl-Eddington chain of reasoning will not lead to a real refinement of our worldview. For this method can never lead to an understanding of the differences between the electrically positively and negatively charged elementary particles.[2] Yours respectfully, A. Einstein 107. From Erwin Schrödinger Zurich, 13 November 1925 Dear Professor, Don’t be alarmed that I am bombarding you with letters.[1] But the implication of those formulas is just too odd. As soon as β , at decreasing temperature, reaches the value , or almost reaches it (up to orders of magnitude ), the free energy, the energy, and the pressure have already assumed the values they also have at the limit for . They are evidently practically temperature-independent in the temperature range between and . The degeneracy hence does oc- cur almost suddenly, according to these formulas, as I had suspected at first.[2] The place , where this happens, is precisely the one where the entropy vanishes according to the entropy formula for the state of an ideal gas (with the Stern-Tetrode constants).[3] Accordingly, this formula would be almost exactly Eik 3 4πe5 /3 ---------------- h2N3 5 -- - mkTV3¹-- 2¸ - -----------------¸ ⋅ = © ¨ ¨ § · l 3N 2 ------ -= l T 0= T 0= β 3N 2 ------ -= β 3N 2 ------ -=