This book deals with the entrenched misunderstandings of Feyerabend's philosophy, brings together the positive elements to be found in Feyerabend's work, and presents these elements as a coherent alternative conception of scientific rationality. It is the first book-length study of Feyerabend's post-1970 philosophy and will be an invaluable resource for philosophers of science, students of the philosophy of science, and anyone who wants to understand the views of one of the most influential philosophers of science of the twentieth century.