Maxims, axioms & idioms · a browsable collection

Legal maxims, political axioms, and the idioms that carry them into everyday argument — each with a plain-English gloss and where it comes from. We state what a maxim means and where it's from; we do not tell you it is right. Open any maxim to see the case law that cites or applies it — curated landmark cases plus a live search of the public record. The legal maxims cross-reference the same categories as our case law.

Legal maxims Political axioms Idioms & mottos All

Ignorantia juris non excusat legal · Latin

“Ignorance of the law excuses not”

You are bound by the law whether or not you know it exists.

Provenance: Roman-law maxim; standard in common-law systems.

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Actus reus non facit reum nisi mens sit rea legal · Latin

“An act does not make one guilty unless the mind is also guilty”

Most crimes require both a wrongful act and a guilty mental state.

Provenance: Coke; foundational to Anglo-American criminal law.

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Nemo judex in causa sua legal · Latin

“No one should be a judge in his own cause”

A decision-maker must not have a personal stake in the matter — the rule against bias.

Provenance: Natural-justice maxim; Dr. Bonham's Case (1610).

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Audi alteram partem legal · Latin

“Hear the other side”

No one should be condemned unheard — the core of due process.

Provenance: Roman/natural-justice maxim.

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Stare decisis legal · Latin

“To stand by things decided”

Courts follow prior rulings — the engine of case law.

Provenance: Common-law doctrine of precedent.

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Respondeat superior legal · Latin

“Let the superior answer”

An employer is liable for torts an employee commits within the scope of employment (vicarious liability).

Provenance: Common-law agency doctrine.

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Nulla poena sine lege legal · Latin

“No penalty without a law”

You can only be punished under a law that existed when you acted (anti-ex-post-facto).

Provenance: Enlightenment penal principle; Feuerbach.

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Ei incumbit probatio qui dicit, non qui negat legal · Latin

“The burden of proof is on the one who asserts, not the one who denies”

The party making a claim must prove it.

Provenance: Roman law (Digest).

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Res ipsa loquitur legal · Latin

“The thing speaks for itself”

Some accidents so obviously imply negligence that the fact of them is evidence.

Provenance: Byrne v. Boadle (1863).

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De minimis non curat lex legal · Latin

“The law does not concern itself with trifles”

Courts won't act on trivial matters.

Provenance: Common-law maxim.

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Habeas corpus legal · Latin

“That you have the body”

A court order requiring a jailer to justify holding a prisoner — the great writ against unlawful detention.

Provenance: English common law; U.S. Const. art. I, §9.

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Cui bono legal · Latin

“To whose benefit?”

Ask who profits — a guide to motive.

Provenance: Cicero, quoting Cassius.

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Fiat justitia ruat caelum legal · Latin

“Let justice be done though the heavens fall”

Justice must be done regardless of consequence.

Provenance: Roman maxim; Somerset v Stewart (1772).

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Power tends to corrupt, and absolute power corrupts absolutely political · English

Concentrated, unchecked power reliably degrades those who hold it — the case for checks and balances.

Provenance: Lord Acton, letter to Bishop Creighton, 1887.

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Malo periculosam libertatem quam quietam servitutem political · Latin

“I prefer dangerous liberty to peaceful servitude”

Freedom with risk beats safe subjection.

Provenance: Quoted by Thomas Jefferson (1787); attrib. Count Palatine.

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Salus populi suprema lex esto political · Latin

“Let the welfare of the people be the supreme law”

The good of the public is the highest law — invoked for the state's police power.

Provenance: Cicero, De Legibus.

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A little rebellion now and then is a good thing political · English

Periodic dissent keeps government honest.

Provenance: Thomas Jefferson, letter to James Madison, 1787.

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Sic semper tyrannis idiom · Latin

“Thus always to tyrants”

The motto of Virginia; a declaration against tyranny. (Historically also shouted by Booth at Lincoln's assassination — stated as fact, not celebrated.)

Provenance: Virginia state motto (1776).

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Give me liberty, or give me death! idiom · English

Freedom is worth dying for — a Revolutionary rallying cry.

Provenance: Patrick Henry, 1775 (as later reconstructed).

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No taxation without representation idiom · English

Government may not tax those it does not represent — a founding American grievance.

Provenance: American Revolution-era slogan.

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The whole world is watching idiom · English

Publicity as a check on state violence against protesters.

Provenance: Chicago, 1968 Democratic Convention protests.

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Vox populi, vox Dei idiom · Latin

“The voice of the people is the voice of God”

Popular will carries great authority — though it is usually quoted against its original cautionary sense.

Provenance: Attrib. Alcuin (c. 800), who wrote it to WARN against trusting the crowd.

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