One of the reasons why I like 1 John so much is because it is so richly theological. Some verses are so densely packed with such theological profundity that I could spend (and have spent) hours talking all about just a single verse.
In this respect, I am especially fond of 1 John 5:20, which I translate below:
οἴδαμεν δὲ ὅτι ὁ υἱὸς τοῦ θεοῦ ἥκει, καὶ δέδωκεν ἡμῖν διάνοιαν ἵνα γινώσκωμεν τὸν ἀληθινόν· καὶ ἐσμὲν ἐν τῷ ἀληθινῷ, ἐν τῷ υἱῷ αὐτοῦ Ἰησοῦ Χριστῷ. οὗτός ἐστιν ὁ ἀληθινὸς θεὸς καὶ ζωὴ αἰώνιος.
We know that the Son of God came, and has given us understanding so that we might know the True; and we are in the True, in His Son Jesus Christ. He is the true God and eternal life.It would be well to start at the beginning and perhaps go phrase by phrase.
John begins with the word "we know." This is shocking because he thus describes Christian belief as a kind of knowledge. It is not a totally baseless faith with no grounding in reality at all, nor is it said to be a kind of committed hope which makes no claim to know one way or the other. On the contrary, Christian belief is rightly defined as a kind of knowledge on John's view. Of course, it depends on who are the implicit "we" of this verse. Does it refer to John and the greater apostolic community, standing in the background of this whole epistle (cf. 1 John 1.1-4)? Or rather is it all Christians, both the apostles and those to whom he is writing? The apostolic claim to knowledge is grounded in personal experience, as the opening verses of the epistle demonstrate:
We declare to you what was from the beginning, what we have heard, what we have seen with our eyes, what we have looked at and touched with our hands, concerning the word of life—this life was revealed, and we have seen it and testify to it, and declare to you the eternal life that was with the Father and was revealed to us—we declare to you what we have seen and heard so that you also may have fellowship with us; and truly our fellowship is with the Father and with his Son Jesus Christ.But if the apostles know the truth of what they tell other people, then Christians who believe the apostles at their word likewise can be said to know on the basis of their testimony. This is something we already grant for many people: students who've never set foot near a volcano can know all about the processes of one through the testimony of scientists, recorded in their school textbooks. So also, Christian faith is a kind of knowledge -- not simply a 'secret' knowledge apprehended through a sort of spiritual intuition, but one that is really empirical: it is based on the testimony of the apostles, who knew Jesus, ate with him, learned from him, and saw him risen from the dead.
What is this exact item of knowledge? What is it that Christians know? They know that the Son of God has come -- referring to Jesus of Nazareth. This is what distinguishes Christians from members of other religions, namely what they know about this person Jesus. When John says that Jesus has come, he means to refer to a real life arrival of the Son of God. Not a mythology, not a nice idea, not a religious ideal, but a concrete person who is the Son of God. This is because, as I've already covered, the basis of this knowledge is not some kind of spiritual insight but flesh-and-blood experience in the real world: what he's seen, touched, heard, etc. Whoever says that the New Testament document is all myths, that Jesus never existed, and so on is full of shit, and probably hasn't read much of it. John's claim here is a concrete one about Jesus of Nazareth: he claims to know that this real life person from a specific city in Palestine is the Son of God.
The advent of the Son of God had a specific purpose: to give us understanding so that we might know the True. Some manuscripts here read the true God, but in any case, it is evident that the reference is to God. Jesus comes to us, in other words, in order to teach us what God is like. This clearly assumes that God is otherwise unknowable to us, since there would be no point in coming if we could know what God is like apart from Jesus telling us. And this indeed what Jesus himself says elsewhere in the gospels:
All things have been handed over to me by my Father; and no one knows the Son except the Father, and no one knows the Father except the Son and anyone to whom the Son chooses to reveal him (Matt 11:27).We can know, of course, that God exists, and we can know various things about the way he is related to the world: for instance, that he is immutable and impassible and omnipotent and so on. But the revelation of Jesus tells us something further -- namely, it tells us how this God relates to us, and what he wants and expects of us, and what he has planned for us. If you know that God is immutable and impassible and the rest, you don't yet know what God's relation is to you, or what is the specific way in which God is disposed towards you. Jesus teaches us precisely this.
Of course, the substance of the revelation of the Father in Christ is what John said in the previous chapter:
Beloved, let us love one another, because love is from God; everyone who loves is born of God and knows God. Whoever does not love does not know God, for God is love. God’s love was revealed among us in this way: God sent his only Son into the world so that we might live through him. In this is love, not that we loved God but that he loved us and sent his Son to be the atoning sacrifice for our sins (1 John 4:7-10).The Son of God teaches us about the True in this way: by showing us how much it is, exactly, that he loves us. He loves us so much that he sends the Son into the world so that the dead can live. He loves us so much that he sends his Son to be the sacrifice of atonement for the sins of the whole world. Nothing is uglier than a dead body, except perhaps the dead body of a wretched sinner -- and yet, despite the fact that we are those dead and wretched sinners, God loved us so much that he sent his Son to save us from this state. This proves that not only is God loving, but that he is love. Love is the very essence of God.
So loving is this God, in fact, that he invites us to become a part of him in a sense. We become a part of him through our participation and adoption into the life of the Trinity. We are "in the True" because we are in His Son, as John says. Through our union with Christ, who is the only-begotten Son of God, we too become children of God. One with the Son of God, we lift up praises and thanksgivings to the Father through the Holy Spirit, and in this way we are filled with God. We are in the True because the True makes room for us within himself, through Jesus Christ his Son, to whom we can be united.
This Jesus is not to be thought of as of a different kind than the Father. On the contrary, John says he is the true God. This word "he" most naturally refers to "Jesus Christ," since this is the name which most immediately precedes it. So John is making it clear that the Son is not of a different sort than the Father, but rather is consubstantial with him: the Father and the Son (and the Holy Spirit) share a divine nature, so that there is one God who subsists in three persons.
Finally, Jesus Christ is also called eternal life. John said earlier that God gave us eternal life, and this life is in his Son (1 John 5:11). I understand this as follows: Christ, who is the Son of God incarnate, is the one to whom we must go if we are to find eternal life. If we go to him in faith and repentance, then we will receive eternal life from him. But if we stay far off, we cannot have eternal life left only to our own resources. Yet in some sense, this eternal life is already given to everyone in Christ: the offer of life is given to absolutely everyone, since Christ died to make atonement for the sins of the whole world (1 John 2:2); what remains is only that this eternal life be voluntarily and personally appropriated. This means that Christ, in himself, is eternal life. Ratzinger says that
Christ inflicts pure perdition on no one. In himself he is sheer salvation (Eschatology: Death and Eternal Life, p. 205).Christ will not be the cause or the principle of any person's damnation. Rather, a person is effectively the cause of her own damnation because she refuses the offer of grace in Christ. Christ in himself is only salvation, only goodness, and has nothing to offer anyone except a share in his same mercy and goodness and forgiveness which reaches out to everyone.
Much more can be said, but these reflections serve as the briefest and most incomplete of outlines of a theologically rich exegesis of this tremendous passage from 1 John.