Section: The Circumstances and Indicators of a Narrator’s Truthfulness or Falsehood

Because any given human being may, at times, lie and at other times speak the truth, it is plain that not everyone who conveys reports is invariably truthful, nor is everyone invariably false. Hence, no rational person has ever asserted that every solitary report— or every report issued by a single individual—must, by definition, be true and yield certain knowledge, nor that it must be false. Rather, people realize that a lone report can be accompanied by evidence that proves its veracity; in that case it is known to be true despite coming from only one source. Likewise, proof may appear showing the report to be false, in which case it is recognized as a lie—even if thousands repeat it—when their narrative rests on no real knowledge or on deliberate collusion to fabricate, just as the adherents of erroneous creeds transmit the falsehoods they themselves believe.

When, however, the transmitters speak on the basis of genuine knowledge of the matter, they are in reality truthful. Their truthfulness is sometimes established by the harmony of their reports without any prior agreement, even if the informants are only two. For if two individuals, independently and without collusion, relay a lengthy account that each traces back to his own knowledge— and if such a detailed concurrence in lying or mistake would normally be implausible—then the report is known to be true.