In very recent times humanity has learnt a vast amount about the universe, the past, and itself. But through our remarkable successes in acquiring knowledge we have learned how much we have yet to learn- the science we have, for example, addresses just 5 per cent of the universe; pre-history is still being revealed, with thousands of historical sites yet to be explored; and the new neurosciences of mind and brain are just beginning. What do we know, and how do we know it? What do we now know that we don't know? And what have we learnt about the obstacles to knowing more? In a time of deepening battles over what knowledge and truth mean, these questions matter more than ever. Bestselling polymath and philosopher A. C. Grayling seeks to answer them in three crucial areas at the frontiers of knowledge- science, history and psychology. A remarkable history of science, life on earth, and the human mind itself, this is a compelling and fascinating tour de force, written with verve, clarity and remarkable breadth of knowledge.