Didymus the Blind : As one confessing God in word alone, he denies him with his deeds. This is "knowing Jesus" according to mere opinion. Therefore, it is no paradox if the evil spirit says to the Jewish exorcists, "I know Jesus" and the following, just as other demons used to say, with a loud cry, to Jesus himself, "I know who you are, the Holy One of God." To these you can add the passage, "even demons believe and they tremble," for it provides no evidence that evil spirits have faith accounted as righteousness. We must also say with regard to our current passage that just as those who receive cures from Jesus do so according to their faith, so those calling on Jesus for the expulsion of a demon or for another cure accomplish this in accord with the faith they have. Here, however, the evil spirit says, "Who are you that call on Jesus, for I do not perceive the power that I have often experienced when his name is called." — CATENA ON THE ACTS OF THE APOSTLES 19.13