I have been reading through Joseph Ratzinger's Introduction to Christianity, and I have found it very helpful and edifying. It is especially impressive and encouraging to see this brilliant theologian of our times expressing ideas and notions that I had thought of myself, prior to having read him. One particular idea comes to mind, and that is the way I have understood this verse from 1 John:
and [Jesus] is the atoning sacrifice for our sins, and not for our sins only but for the sins of the whole world (1 John 2.2).
I found it significant that John here does say that the atoning sacrifice for our sins is Christ's death in isolation from his life, but rather it is Christ himself. He makes the whole identity of Jesus to consist in advocacy on behalf of sinners and making atonement for their sins. If you want to know what it means to be Jesus, the answer is simple: Christ's personal identity is to advocate on behalf of sinners and to make atonement for them.
And in Introduction to Christianity, he goes into greater depth about this aspect of Christ's being. He says in effect that Christ's existence is fundamentally relational, not atomic, at heart: the Son comes from the Father and is totally obedient to him, and he is open to all people in his love which calls all people to himself.
To John, "Son" means being from another; thus, with this word he defines the being of this man [i.e., Jesus] as being from another and for others, as a being that is completely open on both sides, knows no reserved area of the mere "I". When it thus becomes clear that the being of Jesus as Christ is a completely open being, a being "from" and "toward", which nowhere clings to itself and nowhere stands on its own, then it is also clear at the same time that this being is pure relation (not substantiality) and, as pure relation, pure unity (Ratzinger 2000, pp. 186-7).
Christ is thus understood as having a purely relational being. For Christ, there is openness on both sides: openness to God the Father, so as to obey him perfectly in everything; and openness to all people, because he loves all people and makes himself available to them, at the same time willing that all should come to him and being unwilling to cast anyone away (cf. John 6:37). Ratzinger therefore describes Jesus' being as consisting in "from" and "towards": he is from the Father, so that his life consists in obedience to the Father's mission; and he is towards others, in the sense that he always acts for the sake of others.
All of this is implicit in the analysis I gave above of 1 John 2.2, for after all, if Christ's life consists in making atonement for sinners, he certainly does this at the behest of his Father: Indeed, God did not send the Son into the world to condemn the world, but in order that the world might be saved through him (John 3.17). So if Christ's being is utter openness to other people, making atonement for them and working to save them, then it is also utter openness to the Father, a willingness to obey the Father for the salvation of the world even to the point of death on the cross (cf. Phil 2).
Jesus Christ, then, is he who saw the meaning of human existence, not in power and self-assertion, but in existing utterly for others -- who indeed was, as the Cross shows, existence for others -- to him and to him alone God has said, "You are my son, today I have begotten you" (Ratzinger 2000, p. 219). Christ is the man who can embrace all men because he has lost himself and them to God (p. 243).
Now what does this mean for Christians? Well it is evident that whoever says "I abide in [Christ]," ought to walk just as he walked (1 John 2.6). Christ not only acts for our salvation and demonstrates his character for us, but he also gives us the model of what a true human life ought to look like. He gives us the example of how it is that we ought to live our own lives: in utter openness to God, submitting to his will in everything, and in utter openness to others, in love for all and willing to help all. Ratzinger writes:
To John, being a Christian means being like the Son, becoming a son; that is, ,not standing on one's own and in oneself, but living completely in the "from" and "toward". Insofar as the Christian is a "Christian", this is true of him. And certainly such utterances will make him realize to how small an extent he is a Christian (2000, p. 187).
So being a Christian, in a sense, is being empty -- empty, that is, of any substantial "I", a closed-off space which marks a limit on God's claims to our obedience, or others' claims to our love. Nothing like that exists in Christ: he is utterly obedient to the Father in everything, and utterly open to everyone in his love for all. And this is essential for Christian unity:
Our reflections have shown that Christian unity is first of all unity with Christ, which becomes possible where insistence on one's own individuality ceases and is replaced by pure, unreserved being "from" and "for". For such being with Christ, which enters completely into the openness of the one who willed to hold on to nothing of his own individuality (cf. also Phil 2:6f.), follows the complete "at-one-ness" -- "that they may be one, even as we are one." All not-at-one-ness, all division, rests on a concealed lack of Christliness, on a clinging to individuality that hinders the coalescence into unity (2000, p. 187).