This book examines and compares the two major traditions of thought that have attempted to incorporate institutions within economics. These are the "Old" (or American) Institutionalist tradition of Veblen, Mitchell, Commons and Ayres, and the "New" Institutionalism that has developed more recently from neoclassical and Austrian sources. The discussion is organized around a set of key problems involving the use of formal or nonformal analytical methods, individualist or holistic approaches, the respective roles of rational choice and rule following behavior, the relative importance of spontaneous evolution and deliberative design of institutions, and questions relating to the normative appraisal of institutions.