People will often be persuaded by a credible man, but when two, three, or four good men agree about something, the issue is thought to be beyond debate, and thus often they are all led astray, either by all erring in judgment at the same point, or by too credulously deferring to the testimony of one. Even if ten people offer the same testimony, if it turns out that their knowledge comes from only one of them, then we should treat their testimony as if there had only been one of them.
