Karen Hunger Parshall, a senior historian of mathematics, offers the first biographical study of James Joseph Sylvester and his work. A brilliant Cambridge student at first denied a degree because of his faith, Sylvester came twice to America to teach mathematics, ultimately becoming one of Daniel Coit Gilman’s faculty recruits at Johns Hopkins in 1876 and winning the coveted Savilian Professorship of Geometry at Oxford in 1883. He held professorships of natural philosophy, worked as an actuary, was called to the bar, and taught mathematics to cadets training for engineering and artillery posts in the British Army. During his long, distinguished career he also edited England’s Quarterly Journal of Pure and Applied Mathematics and established the American Journal of Mathematics , the first sustained mathematics research journal in the United States. Situating Sylvester’s life within the political, religious, mathematical, and social currents of nineteenth-century England, Parshall penetrates the myth of this venerated figure, revealing how he lived, the choices he made and why, how the world in which he lived affected him - and how he affected that world. The story of Sylvester’s life sheds light on the evolution of mathematical thought. It also examines the ways in which mathematics may be done and what factors may shape the mathematician’s ideas. Parshall explores the development of academic professionalization, nineteenth-century mathematical culture, and the emergence of modern algebra as a mathematical discipline. She highlights the human side of what many view as that most arcane and otherworldly of intellectual endeavors, mathematics, which indeed answers to such diverse factors as religion, ego, and depression.