I have never encountered an introductory text like this one. As far as textbooks go, it is distinctive. It attempts to present a side of philosophy that has been hidden from the view of all but its practitioners. Real philosophy can be formal and rigorous in the very same ways in which mathematics and physical science are formal and rigorous. Glymour's book should make a good many people proud to be philosophers in the twentieth century."- Douglas Stalker, Associate Professor, Department of Philosophy, University of Delaware