Common law got its name from being common to the English king's courts
After 1066, Norman kings built courts whose rulings applied across all of England, slowly pushing aside local folk and manor courts. That shared, judge-made law spread through the British Empire. Today about a third of the world's people live under common law or systems blending it with civil law.
The engine of common law is precedent. Under stare decisis, Latin for standing by what has been decided, a court facing a case like an earlier one follows the reasoning already laid down. When a truly novel dispute arrives, a so-called case of first impression, judges settle it themselves and create a fresh precedent for others to follow.
The phrase has piled up meanings. It first described the law of the royal courts as opposed to local tribunals, then came to mean judge-made law as opposed to statutes, and later labelled whole legal systems descended from England's, as opposed to civil law countries. It is also contrasted with equity, the separate rules developed by the late medieval Court of Chancery, and with the law of England's church courts. William Blackstone described it as unwritten law resting on immemorial custom accepted throughout the kingdom.
The modern understanding owes a surprising debt to a critic. Jeremy Bentham coined the phrase judge-made law while attacking the common law's legitimacy, and the practice of treating case law as binding precedent grew out of that assault, replacing older theories that judges merely declared existing law. Working out what the law says now involves establishing facts, finding relevant statutes and cases, and extracting principles to predict how the next court will rule.
American judges shaped the philosophy. Oliver Wendell Holmes Jr. argued that general principles emerge gradually from countless specific decisions and that experience, not pure logic, drives the law; in The Path of the Law he condemned keeping rules merely because they dated from the reign of Henry IV. Benjamin Cardozo described the method as inductive, building generalisations from particulars. That incremental style contrasts with legislation, which must pass through committees, debates and votes. Legislatures can override common law rights, and courts then interpret the statute's purpose.
Source: Common law
