In the Fourth Gospel, Jesus makes various I-am-[something] statements — I am the bread of life; I am the true vine; I am the good shepherd; I am the way and the truth and the life. In context, the meaning of these statements is clear. Jesus is not coolly delivering academic pronouncements about how we get to God. No, he is importuning the skeptical crowds (and sometimes his skeptical disciples) with familiar metaphors; he is portraying himself in terms that might catch his audience's attention, the better to bolster his claim of legitimacy and authority.
Jesus' approach here isn't unlike the way many Republicans' campaign ads trumpet how conservative they are. And Jesus uses this approach for a similar purpose: it's part of his effort convince people that he is something they approve of, and so they should pay attention to him and do as he is urging.
In effect, Jesus is saying: "OK, you're all wondering: Who is this guy? Well, you know these good things I've been describing? The bread of life, the true vine, the good shepherd, the way and the truth and the life? That's what you get with me; I'm the real deal, not just some itinerant trickster from Nazareth."
The Bread-of-Life Metaphor: Importuning the Crowd
For example, take the bread-of-life passage in John 6.25-60. Jesus gets his disciples to feed the 5,000, but then heads for the mountain, because the crowd was going to make him king by force.
The crowd doesn't hold still for this. If you're going to have a king, a guy who can miraculously feed 5,000 people should certainly be a good candidate. The next day, the crowd tracks down Jesus on the other side of the lake.
Jesus dresses them down: You've got it all wrong, people. It's not about the earthly bread I just gave you. It's about the eternal life that I'm bringing you, with the approval of God himself.
The crowd responds: Yeah? So what do we need to do, to do what God requires?
Jesus says: You must believe in the one he sent. (He means himself, of course.)
The crowd reacts skeptically: Whoa! Sure, you gave us bread and fish, but eternal life, just from believing in you? That's something else entirely, pal. Why should we believe you? Show us some kind of sign — some corroborating evidence, the way God gave our forefathers manna from heaven. (Evidently the crowd didn't think the mass feeding was enough, which says something in itself.)
Jesus responds: You're getting a sign already — God is giving you bread from heaven that gives life to the world.
The crowd, still skeptical (and still focused on what they want), demands: Fine; from now on, give us that bread.
Jesus responds: You still don't get it, do you? Open your eyes, people; I am that bread! What you get with me is precisely what you say you're looking for.
The crowd doesn't buy it. They grumble and say: Wait just a minute. This is Jesus from the block, the son of Joseph. We know this guy.
Jesus continues to argue his case. The bread of life, he says? It's me. But even his disciples gripe about how hard a teaching it is. They ask each other who — and by implication, who in his right mind — can accept the teaching.
The Way-Truth-Life Metaphor in Context: Jesus Was Wrapping Himself in the Father's Mantle
Now consider the way-truth-life saying in John 14. Look at it in context. Is Jesus teaching a lesson about who he was? No. Is he preaching a sermon about salvation? No.
What Jesus is doing here is trying to give his disciples a pep talk. It happens at the Last Supper. That must not have been a particularly happy occasion. "The Jews" had recently tried to stone Jesus (Jn 11); that had to have been frightening for everyone involved. To make matters worse, Jesus knows what's soon going to happen to him; he's troubled in spirit about his upcoming betrayal; and the disciples are obviously perturbed too (Jn 13). It sounds like a pretty depressing dinner, doesn't it?
Jesus tries to buck up his followers: Don't let your hearts be troubled; trust in God, and in me too. I'm going to prepare a place for them in his Father's house, where he'll bring them after he returns. You know the way to where I'm going, he says.
The skeptical Thomas challenges Jesus (as he would do again a little more than a week later): We don't know where you're going, boss; how can we know the way?
Jesus snaps back with a peremptory assertion of his authority: I am the way and the truth and the life. No one comes to the Father except through me.
But notice what comes immediately afterwards: A defense of his legitimacy by painting himself in terms of the Father. If you really knew me, you'd know my Father as well, because the words I've been saying and the things I've been doing aren't just mine, they're the Father's words and deeds in me. From now on, you do know the Father, and you've seen him — got it?
(Emphasis is mine of course. And while we have no record of Jesus saying, "got it?" it certainly fits the general tenor of the Fourth Gospel's account. We can imagine Jesus angrily jabbing his finger at Thomas.)
Philip puts forth an olive branch: Just show us the Father, Lord; that'll be enough for us. Jesus turns and tears a strip off of Philip's hide too: Don't you know me, Philip, after I've been among you such a long time? How can you say, show us the Father — don't you believe I'm in the Father, and the Father is in me?
This isn't a Jesus who is dispassionately announcing a technical point about salvation. This is a Jesus who is passionately trying to prove his legitimacy and authority; who is trying to hold his disciples together, to keep them from drifting away in the middle of an incredibly stressful situation.
So what about Jesus' claim that no one comes to the Father except through him? If we read it in context, it's clear we shouldn't take it literally. At most, we should read it metaphorically: When Jesus has been preaching and working miracles, it's been the Father acting through him; and that which he has been preaching — loving God above all, loving one's neighbor as one's self, and amending one's life when necessary — is the only way to the Father. That's considerably different than the traditionalist Christian claim that the only path to salvation is supposedly "believing in Jesus," whatever that means.
(All this assumes, arguendo, that Jesus actually said these things in the first place. That's not at all convincingly established by the evidence.)