Letter from Albert Einstein to Elie Cartan - 21 June1950

June 21,1950 Professor Elie Cartan 95 Boulevd Jourdan Paris 14, France Dear Mr.Cartan: I felt very strongly with you when I received notice of the great loss you have suffered recently. In these trying situations one feels stronger than ordinarily how difficult it is for a human being to hold fast to the notion - so inescapable to a physicist- that the Now is only an illusion, not something pertaining to reality. Several colleagues have drawn my attention to the fact that - already in the beginning of the twenties - you proposed to introduce non-symmetrical fields to generalize relativity theory. I have found in the last years that it is very natural indeed to find on this basis general equations for the field. It seems, however, extremely difficult to find out if the whole thing is conform to physical reality. One thing I have no doubt about, namely that any scheme of physics based fundamentally on the probability concept will show itself unacceptable eventually. With my cordial greetings and wishes, yours sincerely, Albert Einstein