3 3 2 D O C U M E N T S 3 4 8 , 3 4 9 D E C E M B E R 1 9 2 8 348. To Arthur LeRoy Cohen[1] [Berlin,] 26 December 1928 Dear young man, In your article[2] you have very correctly explained that we can experience and represent movement only as relative movement. This was already known to the ancients and was also accepted by all the opponents of relativity theory. However, until the appearance of the general theory of relativity, it seemed that the concept of absolute movement was necessary for the formulation of the laws of movement. The problem of the theory of relativity was to disprove this. Your question, how the world was created if there was only one body in it, cannot yet be definitely answered. We do not know whether space can exist outside this body. But we know this much: it would be meaningless to speak of its movement.— However, it would be better for you to teach others only once you have learned something yourself. Kindest regards, 349. To Ernst Reichenbächer [Berlin,] 26 December 1928 Dear Colleague, The two evaluations are enclosed.[1] Please excuse the pretentious tone, but in such matters, a modest style is not an expedient virtue.— It is very kind of you to have dealt with my new theory so openly. I have made some wonderful progress. Hamilton’s principle has proved not to be a suitable ap- proach for deriving the field equations.[2] When I can, I will send you the proofs of the article.[3]— Meanwhile, best regards, your