'I gradually came to the conclusion that I should prefer a field in which one could hope to know more at the end of one's life than when one had begun.' So wrote Isaiah Berlin toward the end of the Second World War, when he decided to bid farewell to philosophy in favour of the history of ideas. In The Philosophy of Isaiah Berlin Johnny Lyons shows that Berlin's Damascene moment actually led him to a more original and engaging way of being a philosopher, since his approach to intellectual history amounted to the pursuit of philosophy by other means. Recasting Berlin as a philosopher who took humanity and history seriously, Lyons reveals the underlying unity of his wide-ranging and seemingly fragmented ideas. By painting Berlin in this new and more illuminating light, he throws into sharp relief the deep and enduring human interest of his thought. Lyons emphasises aspects of Berlin's thinking that have largely been neglected. These include his recognition of historical contingency and of the importance of truth in human affairs as well as his scepticism about determinism and account of why freedom should be valued. This introduction to Berlin's thought, and particularly its examination of these mainly overlooked views, reveals a new Berlin, one with surprising contemporary relevance to the debates that continue to dominate philosophy, politics and intellectual history today.