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 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.