In the folklore of mathematics, James Joseph Sylvester (1814-1897) is the eccentric, hot-tempered, sword-cane-wielding, nineteenth-century British Jew who, together with the taciturn Arthur Cayley, developed a theory and language of invariants that then died spectacularly in the 1890s as a result of David Hilbert's groundbreaking, 'modern' techniques. This, like all folklore, has some grounding in fact but owes much to fiction. The present volume brings together for the first time140 letters from Sylvester's correspondence in an effort to establish the true picture. It reveals - through the le