Every oath ought to be founded upon certain knowledge.

Explanation

No person may swear to what he does not know; an oath grounded on conjecture, supposition, or hearsay is void.

Where this applies

• Someone swore an affidavit about things they couldn't possibly know firsthand.
• A witness is testifying under oath based on what they heard from someone else.
• The sworn statement is based on guesswork and assumptions, not actual knowledge.

See also

• 9.1.11 Proofs ought to be evident — that is, clear and easily understood.
• 9.2.1 To swear is to call God as witness, and is an act of divine worship.