Of all philosophers of the 20th century, few built more bridges between academic disciplines than Karl Popper. He contributed to a wide variety of fields in addition to the epistemology and the theory of scientific method for which he is best known. This book illustrates and evaluates the impact, both substantive and methodological, that Popper has had in the natural and mathematical sciences. The topics selected include quantum mechanics, evolutionary biology, cosmology, mathematical logic, statistics, and cognitive science. The approach is multidisciplinary, opening a dialogue across scientific disciplines and between scientists and philosophers.