This book sets out to identify the nature and implications of a proper understanding of pluralism in a original and illuminating way. Isaiah Berlin believed that a recognition of pluralism is vital to a free, decent and civilised society. By looking below at the often neglected foundations of Berlin's celebrated account of moral pluralism, Lyons reveals the more philosophically profound aspects of his undogmatic and humanistic liberal vision. He achieves this by comparing Berlin's core ideas with those of several of his most distinguished philosophical contemporaries, an exercise which yields not only a deeper grasp of Berlin and several major twentieth-century thinkers, principally A. J. Ayer, J. L. Austin, P. F. Strawson, Bernard Williams and Quentin Skinner, but, more broadly, a keener appreciation of the power of history and philosophy to help us make sense of our predicament.