Economics is closely related to many other sciences. The whole discussion of value, as we shall see, depends intimately upon considerations of psychology. In fact, the school of economics which has developed farthest the theory of value is often referred to as the Psychological School. Sociology is sometimes defined as the social science, that is, the science of all social relations. If sociology is considered in this sense, 1 economics is a branch of sociology. Other writers hold that sociology deals only with the more general laws which apply to the whole social structure and that it is coordinate with economics and politics and ethics, and not inclusive of them all.

Politics is the science of the state and because of the many and important ways in which the state influences, and is influenced by the manner in which its people make a living, the fields of the two sciences are closely interwoven and have many problems in common. Ethics is the science of moral conduct. It asks the question, what ought to be. There was a time when economists held that economics was concerned only with the question, what is, and not with the question, what ought to be. But to-day practically all economists hold that economics is an ethical science as well as a positive science, that is, it is concerned with what ought to be in the economic sphere, as well as with what is. Just as economics is closely related to the science of politics so it is also closely related to the science of law. Government and law form a framework in which economic forces act.