Conjectures and Refutations is one of Karl Popper's most wide-ranging and popular works, notable not only for its acute insights into the way scientific knowledge grows, but also for applying those insights to politics and to history. It provides one of the clearest and most accessible statements of the fundamental idea that guided his work: not only our knowledge, but our aims and our standards, grow through an unending process of trial and error. Popper brilliantly demonstrates how knowledge grows by guesses or conjectures and tentative solutions, which must then be subjected to critical tests. Although they may survive any number of tests, our conjectures remain conjectures, they can never be established as true. What makes Conjectures and Refutations such an enduring book is that Popper goes on to apply this bold theory of the growth of knowledge to a fascinating range of important problems, including the role of tradition, the origin of the scientific method, the demarcation between science and metaphysics, the body-mind problem, the way we use language, how we understand history, and the dangers of public opinion. Throughout the book, Popper stresses the importance of our ability to learn from our mistakes. Conjectures and Refutations is essential reading, and a book to be returned to again and again.