Since we’ve been debating in the comments to this post just what Lewis was trying to accomplish with his trilemma argument, I thought it might be worth walking through the relevant passages in Mere Christianity step-by-step.
It’s worth recalling that for all the attention it’s received, the argument only takes up somewhere in the neighborhood of five paragraphs. So we should be able to lay it out relatively succinctly.
The argument (or most of it, anyway) appears in book II, chapter 3 of MC, which is titled “The Shocking Alternative.” Earlier in the chapter Lewis has been discussing the Christian view that the world is occupied territory–that, in Lewis’s words, “an evil power has made himself for the present the Prince of this World” (p. 52).* Lewis then considers (1) how this state of affairs can be in accordance with God’s will and (2) what, if anything, God had done about it.
With regard to the first point, Lewis invokes human free will as the explanation for why God’s good creation was able to come under the sway of the devil. Human beings have collectively tried to “set up on their own as if they had created themselves–be their own masters–invent some sort of happiness for themselves outside God, apart from God” (p. 54).
This can never succeed, Lewis says, because we were made to be in communion with God–“He Himself is the fuel our spirits were designed to burn, or the food our spirits were designed to feed on” (p. 54). Because of how we’re made, pursuing happiness apart from God is bound to fail.
So what, in the Christian view, has God done to remedy this sorry situation? Apart from sending Jesus (which we’ll get to in a minute), Lewis said that God has given us conscience, so we can tell that we’ve gotten off the right track; sent us “good dreams: I mean those queer stories scattered all through the heathen religions about a god who dies and comes to life again and, by his death, has somehow given new life to men”; and selected the people of Israel to teach them, and the rest of the world, what kind of God, God is (see pp. 54-5).
Only now after all this set up does Lewis turn to Jesus:
Then comes the real shock. Among these Jews there suddenly turns up a man who goes about talking as if He was God. He claims to forgive sins. He says He has always existed. He says He is coming to judge the world at the end of time. Now let us get this clear. Among Pantheists, like the Indians, anyone might say that he was a part of God, or one with God: there would be nothing very odd about it. But this man, since He was a Jew, could not mean that kind of God. God, in their language, meant the Being outside the world Who had made it and was infinitely different from anything else. And when you have grasped that, you will see that what this man said was, quite simply, the most shocking thing that has ever been uttered by human lips. (p. 55)
Lewis’s claim here seems pretty straightforward: Jesus appeared among the Jews acting like and effectively claiming to be God in the flesh. Now Lewis does not try to establish this point: he seems to be taking, at least for his purposes here, the gospel accounts of what Jesus said and did at face value. Lewis was certainly aware of modern, skeptical biblical scholarship (though he didn’t have a very high opinion of much of it); but for his purposes here he seems to be ignoring the possibility that the gospels don’t accurately record Jesus’s words.
In the following paragraph, Lewis considers the implications of Jesus claiming the authority to forgive sins in particular. He argues that no human being can forgive wrongs done to someone other than himself:
We can all understand how a man forgives offences against himself. . . . But what should we make of a man, himself unrobbed and untrodden on, who announced that he forgave you for treading on other men’s toes and stealing other men’s money? Asinine fatuity is the kindest description we should give of his conduct. Yet this is what Jesus did. He told people that their sins were forgiven, and never waited to consult all the other people whom their sins had undoubtedly injured. He unhesitatingly behaved as if He was the party chiefly concerned, the person chiefly offended in all offences. This makes sense only if He really was the God whose laws are broken and whose love is wounded in every sin. (p. 55)
This seems to be largely an amplification of the point in the previous paragraph: Jesus, at least as he is portrayed in the gospels, claimed, by both word and deed, to act with the authority of God. As Lewis puts is, “[i]n the mouth of any speaker who is not God, these words would imply what I can only regard as a silliness and conceit unrivalled by any other character in history” (p. 55).
In the short paragraph that follows Lewis observes that readers of the gospels–even those hostile to the claims of Christianity–don’t come away with the impression that Jesus is a silly and conceited person. “Christ says that He is ‘humble and meek’ and we believe Him” (p. 55-6).
Only in the final paragraph of the chapter do we get the trilemma argument properly speaking:
I am trying here to prevent anyone saying the really foolish thing that people often say about Him: “I’m ready to accept Jesus as a great moral teacher, but I don’t accept His claim to be God.” That is the one thing we must not say. A man who was merely a man and said the sort of things Jesus said would not be a great moral teacher. He would either be a lunatic–on a level with the man who says he is a poached egg–or else he would be the Devil of Hell. You must make your choice. Either this man was, and is, the Son of God: or else a madman or something worse. You can shut Him up for a fool, you can spit at Him and kill Him as a demon; or you can fall at His feed and call Him Lord and God. But let us not come with any patronising nonsense about His being a great human teacher. He has not left that open to us. He did not intend to. (p. 56)
Given what has gone before, I think we can set out Lewis’s argument so far like this.
1. Jesus, through his words and actions, effectively claimed to be God.**
2. Jesus was either (just) a man, or he was God.
3. If he was just a man, then he was either insane or evil.
Therefore, Jesus was either an insane man, an evil man, or God incarnate.
The argument doesn’t exactly end in this chapter, but continues in the following chapter, “The Perfect Penitent”:
We are faced, then, with a frightening alternative. This man we are talking about either was (and is) just what He said or else a lunatic, or something worse. Now it seems to me obvious that He was neither a lunatic nor a fiend: and consequently, however strange or terrifying or unlikely it may seem, I have to accept the view that He was and is God. God has landed on this enemy-occupied world in human form. (p. 57)
Lewis doesn’t offer further explanation of why it’s obvious that Jesus was neither evil nor insane, though we can imagine that many of his readers (then and since) would be inclined to agree. So, if they take his earlier conclusion as established, then they would probably readily assent to Jesus’ divinity.
After going through this, I think part of the disagreement in the previous comment thread may have been due to different understandings of the scope of the trilemma argument. If we restrict it to just the final paragraph in chapter 3, then its intent does seem limited to the relatively narrow point that, whatever else Jesus was, he wasn’t (just) a great moral teacher. But if you read that as part of a broader argument encompassing the entire back half of the chapter and the first paragraph in the following one, then I think Lewis’s goals are more ambitious. That is, he’s trying to convince the reader that Jesus really was who he claimed to be (or who the gospels claimed he was): God incarnate.
If that’s right, then I stand by my claim that the broader argument has some serious weaknesses–or at least some major undefended premises. But I do think the narrower argument has merit in rebutting a popular image of Jesus as a “great moral teacher.”
*Page references are from the 1996 Touchstone edition published by Simon & Schuster.
**This originally said “claimed to be God,” but as Brandon pointed out, Lewis doesn’t say that Jesus explicitly claimed to be God. Thanks to him for the correction.