In St. John, as in mystical theology generally, the Incarnation, rather than the Cross, is the central fact of Christianity. "The Word was made flesh, and tabernacled among us," is for him the supreme dogma. And it follows necessarily from the Logos doctrine, that the Incarnation, and all that followed it, is regarded primarily as a _revelation_ of life and light and truth. "That eternal life, which was with the Father, has been _manifested_ unto us," is part of the opening sentence of the first Epistle.[62] "This is the message which we have heard of Him and announce unto you, that God is Light, and in Him is no darkness at all." In coming into the world, Christ "came unto His own." He had, in a sense, only to show to them what was there already: Esaias, long before, had "seen His glory, and spoken of Him." The mysterious estrangement, which had laid the world under the dominion of the Prince of darkness, had obscured but not quenched the light which lighteth _every_ man--the inalienable prerogative of all who derive their being from the Sun of Righteousness. This central Light is Christ, and Christ only. He alone is the Way, the Truth, the Life, the Door, the Living Bread, and the True Vine. He is at once the Revealer and the Revealed, the Guide and the Way, the Enlightener and the Light. No man cometh unto the Father but by Him. The teaching of this Gospel on the office of the Holy Spirit claims special attention in our present inquiry. The revelation of God in Christ was complete: there can be no question that St. John claims for Christianity the position of the one eternally true revelation. But without the gradual illumination of the Spirit it is partly unintelligible and partly unobserved.[63] The purpose of the Incarnation was to reveal God _the Father_: "He that hath seen Me hath seen the Father." In these momentous words (it has been said) "the idea of God receives an abiding embodiment, and the Father is brought for ever within the reach of intelligent devotion.[64]" The purpose of the mission of the Comforter is to reveal _the Son_. He takes the place of the ascended Christ on earth as a living and active principle in the hearts of Christians. His office it is to bring to remembrance the teachings of Christ, and to help mankind gradually to understand them. There were also many things, our Lord said, which could not be said at the time to His disciples, who were unable to bear them. These were left to be communicated to future generations by the Holy Spirit. The doctrine of development had never before received so clear an expression; and few could venture to record it so clearly as St. John, who could not be suspected of contemplating a time when the teachings of the human Christ might be superseded.