D O C U M E N T 5 1 4 A P R I L 1 9 2 7 5 1 1 The new results in the area of quanta are indeed very impressive. But in the depths of my soul I cannot warm to the ostrich’s view which is half-causal and half- geometric. I still believe in a synthesis of the quanta and wave approaches, which, I feel, is the only possibility for a definitive solution. Kind regards, your A. Einstein 515. Calculations [Berlin, on or before 5 May 1927] [Not selected for translation.]