A vague and uncertain cause is not a reasonable cause.

Explanation

(English-origin maxim.) A cause of action resting on speculation or conjecture is legally insufficient — the court requires a definite, ascertainable cause before it will hear the case.

Where this applies

• A plaintiff sues a manufacturer claiming 'the product might have been defective, or maybe it was misused' — the court dismisses the claim because a vague, uncertain cause is not actionable.
• A tenant sues a landlord alleging 'something about the building makes me feel unwell' without identifying any specific condition — the court finds no reasonable cause stated.
• A homeowner files a complaint saying the contractor 'probably did something wrong' during the renovation but can't say what — the claim fails for lack of a definite cause.