2 8 8 D O C U M E N T 2 9 5 O C T O B E R 1 9 2 8 295. To Abraham Adolf Fraenkel Berlin, 25 October 1928 Dear Colleague, Mr. Kaluza had the idea, around 1920, of combining gravitation and electricity into a unified entity by treating the world as five-dimensional, but in such a way that all the field quantities would not be variable within the fifth dimension.[1] Whether or not this idea will finally prove itself cannot yet be said. One has to as- cribe to it a certain genius, in any case. A great formal talent is not visible in the publications. It speaks for Kaluza that he has worked under quite difficult external conditions. I have no information about his current position. I can also make no judgments about the extent of his mathematical knowledge and abilities. I can thus not make a specific recommendation. The man makes a good impression in his cor- respondence. Perhaps your colleague at the University of Leipzig, Kowalewski, who once supported granting him a professorship, can tell you some more about him.[2]— Kind regards, your A. Einstein 296. Calculation [??, after 25 October 1928][1] [Not selected for translation.] 297. “Masses, Not Individuals” [Einstein 1929l] Dated [after 25] October 1928 Published 1 January 1929 In: Изобретатель (The Inventor), 1 January 1929, p. 4. [See documentary edition for English translation.]