God is no liar, but these men are slanderers. They admit, they insist, that unregenerate men can speak the truth, even about the Gospel, but they deny that regenerate men can err, even about the Gospel. They even go so far to say that if a man is mistaken in judging another man to be saved, he himself is unsaved. Thus one's own salvation, according to their twisted and Antichristian doctrine, depends on believing the correct things about some sinner's state of mind, and not about Christ. They have added to the Gospel, an error explicitly condemned by Paul.