EINSTEIN--Niels Bohr: "With the death of Albert Einstein, a life in the service of science and humanity which was as rich and fruitful as any in the whole history of our culture has come to an end. Mankind will always be indebted to Einstein for the removal of the obstacles to our outlook which were involved in the primitive notions of absolute space and time." I. I. Rabi: "His real love was the theory of fields, which he pursued with unremitting vigor to the very end of his more than 50 years of active scientific life. This preoccupation is to a large degree the key to his scientific personality. The theory of general relativity was constructed on the basis of a physical observation of the equivalence of inertial and gravitational mass under certain simple circumstances. Beyond that, his guiding principles were his esthetic and philosophical urge for simplicity and symmetry."