But before I begin to speak of God and His works, I must first speak a few things concerning the prophets, whose testimony I must now use, which I have refrained from doing in the former books. Above all things, he who desires to comprehend the truth ought not only to apply his mind to understand the utterances of the prophets, but also most diligently to inquire into the times during which each one of them existed, that he may know what future events they predicted, and after how many years their predictions were fulfilled.