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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 maximsPolitical axiomsIdioms & mottosAll
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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