This book is a revised and expanded edition of the controversial Foundations of the Social Sciences (1989). The author offers his view on the nature of explanation in the social sciences; analysis of mental states that precede actions; systematic comparison of models of behavior based on rational choice with alternative concepts; exploring possible social science borrowings from neuroscience and evolutionary biology; a review of mechanisms for ranking social interactions from strategic behavior to collective decision making. In a provocative conclusion, he insists on the centrality of quality social science in the war against soft (literary) and hard (mathematical) forms of obscurantism.