This is a collection of nineteen essays in the tradition of critical rationalism (as advocated by Karl Popper). All but one of the essays is previously unpublished and the one previously published paper has undergone significant revisions. The first four essays tackle topics in the philosophy of science, the first being an exposition of Popper's views, the others discussing falsifiability, truth, the aim of science, and ceteris-paribus law-statements. Five essays follow concerned with Reason, reasoning and reasons, in which faulty conceptions of theoretical and practical reason are criticised, the nature and uses of argument are discussed, and the rationality of debate, agreement and disagreement are explained. Next, there are two papers on economics, one of which is a substantial critique of the so-called subjective theory of value, the other a brief discussion of entrepreneurial insight. The last section of the book contains a miscellany of eight critical essays in which some errors of contemporary philosophers are exposed regarding issues including the interpretation of Popper's work, the Gettier problem, no-platforming, open-mindedness, homosexual equality, tolerance, philosophical heuristics and the conduct of debate.