This is a philosophical study of concepts that lie at the foundation of antitrust - a body of law and policy designed to promote or protect economic competition. Topics covered are: the nature of competition; the relation between competition and welfare; the distinction between per se rules and rules of reason; agreements; concerted practices; and the spectrum from independent action to collusion. Although there are many legal and economic books on antitrust, this is the first book devoted to the philosophical scrutiny of the concepts that underpin it. No prior knowledge of philosophy is presupposed. The book is primarily directed at students, theorists and practitioners of antitrust, but will also be useful to lawyers, economists, philosophers, political scientists and others who have an interest in the discipline.