This book is the third volume of Sir Karl Popper's long-awaited postscript to the logic of scientific research. Although it was written over forty years ago, it is still as relevant today as it was then: it contains the outline of a new cosmology and questions some of the fundamental assumptions of current physics research. Those who appreciate scholarly disputes and irony in the history of science will find the rare delights awaiting them in this volume, where Popper directly engages with the heart of the current debate in quantum physics. At a time when most serious physicists are inductivists, subjectivists, positivists, and instrumentalists, attempting to anchor these positions in physics, Popper proposes an interpretation of physics.