praecēdēns

Precedent comes from Latin praecēdēns, present participle of praecēdere — prae (before) + cēdere (to go). Something that goes before. In general English, a precedent is any earlier event that serves as a guide or example. In law, it is much more specific: a precedent is a prior court decision that must be followed by courts in similar future cases. This principle — stare decisis (stand by things decided) — is the backbone of common law systems.

The English common law system, developed from the twelfth century onward, relied on precedent because there was no comprehensive written legal code. Judges looked at how similar cases had been decided before and applied the same reasoning. Henry de Bracton's De Legibus et Consuetudinibus Angliae (~1235) was the first systematic attempt to compile English case law. The idea was pragmatic: consistency in law requires that like cases be treated alike.

The United States inherited the precedent system from English common law. The Supreme Court's decisions are binding precedent for all lower courts. When the Court overturns its own precedent — as it did with Dobbs v. Jackson in 2022, overruling Roe v. Wade (1973) — the legal and political consequences are enormous. The power of precedent is that it creates stability. The danger is that bad precedents persist until someone has the authority and willingness to overturn them.

Civil law systems — used in continental Europe, Latin America, and much of Asia — do not rely on precedent in the same way. Judges in France or Germany apply written codes rather than following prior decisions. The division between common law (precedent-based) and civil law (code-based) systems is one of the fundamental fault lines in global jurisprudence. The word 'precedent' carries different weight depending on which side of that line you practice.