Moreover, it has been determined by the doctors of the Church that the longevity of the ancients, before God destroyed the original world by the Deluge, is to be ascribed to a miracle and not to nature; as though God granted to them such length of days as was required for finding out the sciences and writing them in books; amongst which the wonderful variety of astronomy required, according to Josephus, a period of six hundred years, to submit it to ocular observation. Nor, indeed, do they deny that the fruits of the earth in that primitive age afforded a more nutritious aliment to men than in our modern times, and thus they had not only a livelier energy of body, but also a more lengthened period of vigour; to which it contributed not a little that they lived according to virtue and denied themselves all luxurious delights. Whoever therefore is by the good gift of God endowed with gift of science, let him, according to the counsel of the Holy Spirit, write wisdom in his time of leisure (Eccles. xxxviii.), that his reward may be with the blessed and his days may be lengthened in this present world. And further, if we turn our discourse to the princes of the world, we find that famous emperors not only attained excellent skill in the art of writing, but indulged greatly in its practice. Julius Caesar, the first and greatest of them all, has left us Commentaries on the Gallic and the Civil Wars written by himself; he wrote also two books De Analogia, and two books of Anticatones, and a poem called Iter; and many other works. Julius and Augustus devised means of writing one letter for another, and so concealing what they wrote. For Julius put the fourth letter for the first, and so on through the alphabet; whilst Augustus used the second for the first, the third for the second, and so throughout. He is said in the greatest difficulties of affairs during the Mutinensian War to have read and written and even declaimed every day. Tiberius wrote a lyric poem and some Greek verses. Claudius likewise was skilled in both Greek and Latin, and wrote several books. But Titus was skilled above all men in the art of writing, and easily imitated any hand he chose; so that he used to say that if he had wished it he might have become a most skilful forger. All these things are noted by Suetonius in his Lives of the XII. Caesars. CHAPTER XVII OF SHOWING DUE PROPRIETY IN THE CUSTODY OF BOOKS