Over the past 50 years, Peter Achinstein has earned a reputation in the philosophy of science for careful, thought-provoking, and methodologically significant conceptual analyses. This new book matches that reputation: he begins with a detailed analysis a particular notion, speculation, and the clarified concept serves as the glue to hold together the book's wide-ranging discussions. Achinstein also investigates issues of interest for practicing scientists and the ideas of practicing scientists appear frequently in the book. Indeed, two of the most influential (...) philosophers who discussed speculation were also scientists: John Stuart Mill (who was an economist and psychologist as well as a philosopher) and Isaac Newton. Within a crowded literature on the topic, Achinstein offers a book that is novel, rigorous, and helpful for both philosophers and scientists. (shrink)