"Einstein was a world-famous genius and people I knew used to remark, "You spend a good deal of time with Einstein. He has a perfect brain, doesn't he?" Well, I have never known what is meant by a "perfect brain." I do know that Einstein's mind was very human and had many defects. Einstein was far slower than Jancsi von Neumann to derive mathematical identities. His memory could be faulty, at least after 1933. And he was hardly interested in the details of physics. For a man like Edward Teller, developing the details of a physics problem was passionately important. For Einstein, it was not. In all spheres of life, Einstein's greatest pleasure was in finding, and later expressing, basic principles. But Einstein's understanding was deeper than even Jancsi von Neumann's. His mind was both more penetrating and more original than von Neumann's. And that is a very remarkable statement. Einstein took an extraordinary plea sure in invention. Two of his greatest inventions are the Special and General Theories of Relativity; and for all of Jancsi's brilliance, he never produced anything so original. No modern physicist has."