A detailed account of Einstein's childhood and formative years focuses on the intellectual climate of Germany where, before 1919, his trailblazing work on the special and general theories of relativity received widest notice. The author explores the response to the theories by pure mathematicians, who did not have to face the prospect of a fundamental revision of their basic principles, and by physicists and astronomers, who did. Of interest to physicists, academics and students interested in Einstein himself and in the wider history of science and ideas, or in the social and intellectual history of Germany.