Sir Karl Popper (1902 1994) is one of the most controversial and widely read philosophers of the 20th century. His influence has been enormous in the fields of epistemology, logic, metaphysics, methodology of science, the philosophy of physics and biology, political philosophy, and the social sciences, and his intellectual achievement has stimulated many scholars in a wide range of disciplines. These three volumes of previously unpublished essays, which originate in the congress 'Karl Popper 2002' held in Vienna to mark the centenary of Popper's birth, provide an up-to-date examination of many aspects of Popper's life and thought. Volume 1 discusses a variety of topics in Popper's early intellectual history, and considers also some features of his remarkable influence outside philosophy. The second part of the volume contains papers that from different political perspectives tackle problems raised by Popper's principal contribution to political theory, democracy and community, "The Open Society and Its Enemies". Volume 2 deals especially with Popper's metaphysics and epistemology, including his proposal (critical rationalism) that it is through sharp criticism rather than through the provision of justification that our knowledge progresses. Several papers tackle the problem of the empirical basis, and offer decidedly different answers to some unresolved questions. The volume contains also a number of papers evaluating Popper's celebrated, but much contested, solution to Hume's problem of induction. Volume 3 examines Popper's contribution to our understanding of logic, mathematics, physics, biology, and the social sciences, from economics to education. Among the topics covered are: verisimilitude, quantum and statistical physics, the propensity interpretation of probability, evolutionary epistemology, the so-called Positivimusstreit, Popper's critique of Marx, and his defence of the rationality principle as a component of all social explanations.