This book examines how Isaac Newton's reputation was utilized, and altered, by British men of science in biographies and historical studies published between 1820 and 1870. A detailed analysis of these works and the contexts in which they were produced demonstrates the contemporary significance of these portraits for the scientific community. It is, therefore, among a number of recent ‘Reputational studies’ which argue that representations of historical figures reflect the circumstances in which they are created and that the reputations of such figures can be used to legitimate current interests. Because of the fundamental importance of Newton as a scientific icon, uses of his posthumous reputation, whether in science, religion, biography, poetry, art or more popular genres, have long been subjected to analysis. However, this book focuses on the increase of knowledge about Newton's life and character within a fifty-year period and thus offers a far more detailed examination of the motivations and influences of writers on Newton than any of these previous works. The period under consideration is significant for three reasons. First, it saw a sudden expansion in the amount of material relating to Newton that was available to researchers and readers; second, it saw a series of debates in which Newton's personal and scientific character was either central or used as a resource; and third, it was a period that saw important changes for science and its practitioners. These texts appeared against the background of the increasing professionalization, specialization and secularization of science and it is not coincidental that a period that saw the creation of modern science also featured an identifiable debate about the life and character of the most famous of British natural philosophers.