Einstein once said that the "eternal mystery of the world is its comprehensibility". Deutsch, a physicist, has written an immensely impressive study into what Einstein described as this "miracle" of how we understand the universe. For Deutsch it all comes down to one thing: "the quest for good explanations". Scientific theories are the result not of sense data (empiricism) but are, he says, "guesses  bold conjectures". Deutsch argues compellingly that it is the ceaseless criticism and improvement of our explanations of reality that explains the progress that has been achieved since the Enlightenment, not just in science but in society too. For him, this revolution in thinking marked "the beginning of infinity", the point at which we embraced an optimistic and dynamic view of ourselves and what we can achieve. His optimism and faith in rationality appear to be limitless, but this book is truly mind-expanding in a way that few others are: it goes to the heart of how we grasp the true wonder of the universe.