It is in the nature of things that a negative is no proof.

Explanation

(English-origin maxim.) A negative proposition cannot be proved directly; therefore the party who asserts the affirmative bears the entire burden and must produce positive proof.

Where this applies

• The other side is asking me to prove I never signed the document, but you can't prove a negative — the burden belongs to the person claiming the signature is mine.
• A government agency demands that a property owner prove he never polluted his own land — but proving a negative is impossible, so the agency must produce affirmative evidence of contamination.
• An employer accuses a worker of stealing but demands the worker prove she didn't take anything — the worker can't prove a negative, so the employer must produce positive proof of the theft.