Putnam is one of the most influential philosophers of recent times, and his authority stretches far beyond the confines of the discipline. However, there is a considerable challenge in presenting his work both accurately and accessibly. This is due to the width and diversity of his published writings and to his frequent spells of radical re-thinking. But if we are to understand how and why philosophy is developing as it is, we need to attend to Putnam's whole career. He has had a dramatic influence on theories of meaning, semantic content, and the nature of mental phenomena, on interpretations of quantum mechanics, theory-change, logic and mathematics, and on what shape we should desire for future philosophy. By presenting the whole of his career within its historical context, de Gaynesford discovers a basic unity in his work, achieved through repeated engagements with a small set of hard problems. By foregrounding this integrity, the book offers an account of his philosophy that is both true to Putnam and helpful to readers of his work.