John 20:31

Since this Evangelist hath mentioned fewer than the others, he tells us that neither have all the others mentioned them all, but as many as were sufficient to draw the hearers to belief. For, "If," it saith, "they should be written every one, I suppose that even the world itself could not contain the books." Whence it is clear, that What they have mentioned they wrote not for display, but only for the sake of what was useful. For how could they who omitted the greater part, write these others for display? But why went they not through them all? Chiefly on account of their number; besides, they also considered, that he who believed not those they had mentioned, would not give heed to a greater number; while he who received these, would have no need of another in order to believe. And here too he seems to me to be for the time speaking of the miracles after the Resurrection. Wherefore He saith, "In the presence of His disciples." For as before the Resurrection it was necessary that many should be done, in order that they might believe that He was the Son of God, so was it also after the Resurrection, in order that they might admit that He had arisen. For another reason also he has added, "In the presence of His disciples," because He conversed with them alone after the Resurrection; wherefore also He said, "The world seeth Me no more." Then, in order that thou mayest understand that what was done was done only for the sake of the disciples, he added, "That believing ye might have life in His Name." Speaking generally to mankind, and showing that not on Him who is believed on, but on ourselves, he bestows a very great favor. "In His Name," that is, "through Him"; for He is the Life.

After telling us of the incident in connection with which the disciple Thomas had offered to his touch the places of the wounds in Christ's body, and saw what he would not believe, and believed, the evangelist John interposes these words, and says: "And many other signs truly did Jesus in the presence of His disciples, which are not written in this book: but these are written that ye may believe that Jesus is the Christ, the Son of God; and that believing ye may have life through His name." This paragraph indicates, as it were, the end of the book; but there is afterwards related how the Lord manifested Himself at the sea of Tiberias, and in the draught of fishes made special reference to the mystery of the Church, as regards its future character, in the final resurrection of the dead. I think, therefore, it is fitted to give special prominence thereto, that there has been thus interposed, as it were, an end of the book, and that there should be also a kind of preface to the narrative that was to follow, in order in some measure to give it a position of greater eminence.