GENERAL INTRODUCTION Albert Einstein is the preeminent physicist of this century. In a manner com- parable only to Newton before him, he reshaped our understanding of the physical universe. He was also a major public figure, impelled by events to participate in and comment on many of the significant social and political movements of his time. During Einstein's lifetime, the only collected edition of his writings to ap- pear was a Japanese edition of his scientific works, published in 1923. In the foreword he wrote: [E]s [hat] stets einen eigentümlichen Reiz, das Werden der Theorien zu verfolgen an Hand der Originalabhandlungen und nicht selten verleiht ein solches Studium einen tieferen Einblick in die Materie als eine durch die Arbeit vieler Zeitgenossen geglättete systematische Darstellung des fertigen Gegenstandes. The Collected Papers of Albert Einstein provides a new and comprehensive resource for readers interested in tracing the development of Einstein's ideas and activities through the original documents. This edition will present Einstein's complete writings and correspondence, and related material impor- tant to understanding his work, his life, and his times. It will combine the holdings of the Einstein Archive with material found as the result of further searches. The Archive originally consisted of the papers left by Einstein in the care of the Trustees of his Estate, Dr. Otto Nathan and Miss Helen Dukas, who devoted themselves tirelessly for a quarter of a century to organizing the con- tents and to adding new material. Einstein made no systematic attempt to preserve his papers before about 1920. Prior to that time, he routinely dis- carded manuscripts of published articles, and very few have been preserved. Einstein saved few letters addressed to him, though, fortunately, many of his correspondents kept the letters they received. Only a handful of early note- books, containing lecture and research notes, have survived. After Einstein's dramatic rise to prominence at the end of 1919, his step- daughter Ilse, the first of his secretarial assistants, began to help him with his vastly increased correspondence. The earliest evidence of Einstein's concern