The common law is a system of principles and rules grounded in universal custom or natural law and developed, articulated, and applied by courts in a process designed for the resolution of individual controversies. In this general sense, the common law is the historic basis of all Anglo-American legal systems. It is also an important element in the origin and plan of the United States Constitution.
Though sometimes characterized as "unwritten" in reference to their ultimate source, the principles and rules of the Anglo-American common law are in fact found in thousands of volumes of written judicial opinions reporting the grounds of decision in countless individual cases adjudicated over the course of centuries. The process that produced this body of law has three important aspects. First, common law principles and rules derive their legitimacy from the adversary process of litigation. They are valid only if they are HOLDINGS, that is, propositions necessary to the resolution of actual controversies. Second, the common law is applied through a characteristic reasoning process that compares the facts of the present case to the facts of earlier cases. The holdings of those earlier cases are PRECEDENTS, which must be followed unless their facts can be distinguished or unless they can be overruled because their grounds are deemed unsound in light of changing social conditions or policy. In the latter situation, or if no existing precedent is applicable, a new rule may be fashioned from the logic of related rules or underlying principle. Third, the common law is a process in the procedural sense. Litigation is governed by rules designed to shape issues of fact and law so that a case may be fairly and efficiently presented to and decided by the jury, the traditional mode of trial.
The principles and rules of the common law grow and change within this threefold process at the initiative of parties to litigation as they bring forward issues falling outside, or challenging, existing precedents. The common law may also be changed by legislative enactment, but in Anglo-American countries legislation is relied on chiefly to supplement or revise or codify the common law in specific situations.
The Anglo-American common law evolved from decisions of the three great English courts of King's Bench, Common Pleas, and Exchequer, which were firmly established by the end of the thirteenth century. These courts, though created under...