The law requires, not conjecture, but certainty.

Explanation

(English-origin maxim.) A verdict or ruling may not rest on conjecture — the evidence must establish the facts with reasonable certainty before a party may recover.

Where this applies

• A jury awards damages based on a plaintiff's guess about lost profits rather than actual financial records — the appellate court reverses because the law requires certainty, not conjecture.
• A prosecutor asks the jury to convict based on what 'probably happened' rather than proven facts — the court instructs that conjecture is not a substitute for evidence.
• A claimant seeks compensation for emotional distress but provides only vague assertions with no corroborating testimony — the court finds the claim rests on conjecture, not certainty.