This text consists of 13 occasional pieces (lectures, seminar contributions, radio broadcasts and magazine articles) spanning the years from 1958 until 1993, all of which are published here in English for the first time, except two previously unpublished talks delivered in English towards the end of Karl Popper's life. The volume is divided into two parts; theory of science, and history and politics. The first contains three pieces on Popper's key scientific interests, namely the evolution of human knowledge, his views on the body-mind problem and a lecture on Kepler, on the anniversary of his death. The second part consists of talks and articles on other characteristic preoccupations of the late Karl Popper; the theory of liberty and democracy; whether there is a meaning in history; the significance of the collapse of communism; and the title piece on Popper's conception of life as a trial-and-error process of problem solving. The book presents an insight into the diversity of Popper's key interests throughout his life; the origins of Germanic language and culture; the development of Popper's formulations in the theory of science; and Popper's view of the state of the world at the end of the Cold War and after the collapse of communism.