The Calculus of Consent: Logical Foundations of Constitutional Democracy is a book published by economists James M. Buchanan and Gordon Tullock in 1962. It is considered to be one of the classic works from the discipline of public choice in economics and political science. This work presents the basic principles of public choice theory. Overview The analytical approach of the authors is based on methodological individualism - collective action is composed of individual actions and on the rejection of any organic interpretation of the state. A purely individualistic conception of collectivity is maintained: the state is an artifact, created by men and thus subject to change and perfection. Buchanan and Tullock maintain that only constitutional changes, which can be shown to be in the interest of all interested parties, can be judged as "improvements" and therefore consider conceptual unanimity as the only legitimate decision-making rule. The authors analyze the traditional political science approach to voting systems, including majority voting as the standard as opposed to the unanimity rule. They show that none of those systems is perfect, since there is always a tradeoff: a simple majority-based system imposes varying amounts of both external costs and decision-making costs a unanimity-based system has little or no external costs, but considerable decision-making costs. They conclude that decisions with potentially high external costs should require unanimity or at least supermajority systems. While many political scientists define the political process as a system in which the policy decisions are viewed as a private interest vs. public interest struggle, Buchanan and Tullock suggest that the public interest is simply the aggregation of private decision makers. They show that in classical political science theory, the "public interest" is always the correct choice with the same appeal to all voters, which may or may not be opposed by "special interests". But that theory ignores the fact that most choices appeal to many different "law consumers" with varying strengths. An illustrative example is a choice whether to increase funding for health care. Some voters will strongly support or oppose it, but many may not care at all. They compare this to a market transaction, where the voters strongly desiring better health care could purchase the acceptance of the opposition and uninterested voters with concessions, resulting in an efficient allocation of resources, increasing the happiness of all parties (Pareto optimality). However the equivalent of this in the political realm is