1 8 4 D O C U M E N T S 1 8 6 , 1 8 7 M A Y 1 9 2 8 186. To Paolo Straneo[1] Berlin, 8 May 1928 Dear Colleague, As a result of a long illness, I am only today able to answer your kind letter.[2] I indeed do remember having seen you as a student.[3] I have noted your work, espe- cially what you wrote on the axially symmetric gravitational field, with much interest.[4] I enclose some of my articles here. I would in particular like to direct your attention to the theory of Kaluza.[5] In my considered opinion, the relationship between gravity and electricity remains an unsolved problem in spite of all the ef- forts made to solve it, and it is the most important open problem in this field. I re- main rather skeptical of quantum mechanics, in spite of its great successes. I find its renunciation of causality unbearable.[6] With best regards, your A. Einstein P.S. I can send you the articles only after I have fully recovered from my heart problems. 187. To Antonina Vallentin[1] [Berlin,] 8 May 1928 Dear Mrs. Vallentin, From my personal standpoint I have no objections to becoming a member of the committee to be formed.[2] I also think that with regard to other countries, this would not be inadvisable. On the other hand, I fear that seen from the point of view of domestic politics, this step may not be advisable. People from the right wing here could be upset by it. In particular, it would also be good not to include many Jews in order to spare the project’s internationalism scare quotes.[3] As I said, I would like to mention this for your consideration, but I maintain my acceptance in the event that you and your friends do not share my reservation. Respectfully yours,