In claims for unlawful arrest and detention, prescription commences to run from the date of arrest, not from the date of acquittal or setting aside of conviction. For purposes of section 12(3) of the Prescription Act 68 of 1969, a creditor has knowledge of 'the facts from which the debt arises' when he knows of the arrest and detention and the identity of the debtor (the state). Knowledge that the conduct is wrongful or actionable is a legal conclusion, not knowledge of a fact, and therefore falls outside section 12(3). The debt becomes due when the plaintiff acquires a complete cause of action - in unlawful arrest cases, this occurs at the moment of arrest because every deprivation of liberty is prima facie wrongful. The plaintiff need only plead that he was arrested and detained; the burden shifts to the defendant to prove justification. A plaintiff does not need to wait for the outcome of criminal proceedings before prescription begins to run, as the material facts founding the debt are in place at the time of arrest.