The law shapes politics, economics, history and society in many ways. It regulates the conduct of individuals and businesses, defines their rights and obligations toward each other and with the environment, and serves as a mediator between people. A legal system may be based on written or unwritten documents, on custom or tradition, or on the enacted laws of a particular time or place. Law is a highly complex phenomenon and an ongoing source of debate and controversy. Its nature varies according to the context in which it is discussed and is often influenced by a specific culture or religion. The philosophy of law focuses on explaining how it differs from other normative domains, such as morality or social conventions, and what makes it intelligible.

A major focus of debate about law is its coercive aspect. Early legal positivists, such as Bentham and Austin, maintained that the monopolization of force by the state was an essential characteristic of law, distinguishing it from other normative domains. However, twenty-first century legal positivists like Joseph Raz have tended to deny that the coercive element is necessary or even pivotal to law’s ability to perform its functions in society.

In a democracy, a system of law is usually created by elected representatives and enforced by a judiciary. The legislative branch lays down the laws in terms of specific principles and policies. The executive branch carries out the day-to-day operation of government and administers the laws, and the judicial branch decides disputes between people or between government agencies. This division of power into three branches is known as the separation of powers and forms the basis of the U.S. Constitution.

The scope of law varies considerably from country to country and is largely dependent on the political landscape in each nation-state. While most countries have some form of constitutional democracy, the distribution of political and military power in a given country often influences the shape of their laws. For example, the United States has a constitutional democracy but is a republic in practice, allowing the executive and judicial branches of the federal government considerable independence from the legislature.

Contract law regulates agreements for the exchange of goods or services, and includes laws about insurance, taxation, bankruptcy, commercial transactions, transportation and communications. Criminal law deals with a wide range of offenses and penalties, including the death penalty. Family law covers marriage, divorce and child custody issues. Property law defines people’s rights and duties in relation to their tangible possessions (such as land or buildings) and intangible assets (like stocks and bank accounts).

The study of law also involves a variety of philosophical and theoretical problems, such as the relationship between morality and the law, and whether the legitimacy of the law depends on its being based on some kind of social consensus. This debate is often conducted through the lens of the philosophy of law, which analyzes the concepts of legal intelligibility and the justification of the law.