John the Apostle

John outlived all the other apostles and may have lived into his 90s, which is why his student Polycarp could still teach Irenaeus in the late 100s. Without that long lifespan the apostolic chain breaks. He also wrote (or stands behind) the most theologically dense parts of the New Testament — the Fourth Gospel, the letters of John, Revelation — texts that read more like meditation than history. Almost every later mystical and contemplative tradition in Christianity reaches back through John.