This book results from three convictions: (1) that pressing social problems such as poverty, discrimination, and inequality are not simply the result of individual characteristics but result instead from larger social structures; (2) that scientific methods are the most powerful tools available for replacing superstition and prejudice with knowledge and thus that we can and ought to study those social structures with the methods of the natural sciences, broadly construed; and (3) that philosophy of science can contribute to developing such a science of society, but only if it eschews a priori armchair theorizing in favor of a philosophy intimately tied to the real practice of social science research. The first two convictions have their origin in the Enlightenment. However, the more direct cause in my case was growing up in an era flush from the discoveries of Watson and Crick and a personal involvement in the political movements of the 1960s and 1970s. The third, more cerebral conviction has more recent origins. It results not only from the philosophical arguments of Kuhn and Quine but also from a growing frustration with my philosophical colleagues who are willing to pronounce entire domains of social inquiry doomed to failure while paying little attention to what social scientists actually do.