Here is a formal statement of the argument:
- Premise: Jesus claimed to be Lord.
- Conclusion: Either Jesus is a liar, a lunatic, or Lord.
- Premise: Jesus was not a liar.
- Premise: Jesus was not a lunatic.
- Conclusion: Jesus is Lord.
2. Conclusion: Either Jesus is a liar, a lunatic, or Lord.This is meant to be an exhaustive list of possibilities, but it isn't. If we want to create an exhaustive list of possibilities, we must start with a logical tautology, such as "Either P or not P". Here we can say, "Either Jesus is Lord or he isn't." If Jesus isn't Lord, we can further subdivide the possibility by saying, "Either Jesus was lying or was not lying." This is the underlying reasoning behind this conclusion, but there is a glaring mistake! If Jesus is not Lord, nor was he lying, does that really imply that Jesus was a lunatic?
Here's a lesson that belongs in the first few minutes of Skepticism 101: There are quite a number of ways for a sane person to have a wrong belief! We even have names for them: confirmation bias, logical fallacies, post hoc reasoning, cognitive dissonance, general ignorance, etc. But even if you didn't know what all those were, you would still know that everyone makes mistakes, has wrong beliefs, and sometimes changes their mind about said beliefs.
If you think that being Lord is too wild a belief for anyone to fool themselves about, you obviously haven't had much experience with skepticism. Ever heard of homeopathy? Listened to physics crackpots? Encountered 9/11 truthers? These are smart people, large groups of people, people who are every bit sane, and they believe in junk. I am no longer surprised. I am especially unsurprised that someone can honestly believe they are God. After all, here we are, only a few mistakes away from thinking that Jesus must be God, so how hard could it be? It only needed to happen to one person in two millenia, but I'm sure it's happened to plenty of people in that time.
4. Premise: Jesus was not a lunatic.This premise essentially relies on an emotional appeal. No one wants to think anyone is a loony. Least of all does anyone want to think Jesus is a loony. I for one, would want to be absolutely sure before even considering the possibility that someone is mentally handicapped. But I would also hesitate to insult the mentally handicapped by making assumptions about what they can and cannot do. We must face the logical possibility.
But recall that I said that "lunatic" is not an exhaustive possibility. Jesus could easily have been honestly mistaken. This possibility is easier to swallow, and is also much, much more likely. The only reason "lunatic" is used in the argument rather than "mistaken" is because it has much more emotional punch. In other words, the trilemma argument uses flawed reasoning in order to better play with people's emotions. Shameful.
3. Premise: Jesus was not a liar.This premise is also based on emotional appeal. It's usually accompanied by exhortations to spit upon liars and so forth. I happen to think this possibility is far less likely than the "honestly mistaken" one, but it must nevertheless be considered a possibility. I'm not sure how you would tell if he was a liar anyways. Liars can be nice, you know. They can be hypocrites. Out of billions of people, there only need be one. And no, entertaining the mere possibility that someone is lying doesn't mean you have to spit at them. That's a little extreme, and in poor taste.
1. Premise: Jesus claimed to be Lord.The trilemma is still not exhaustive, because there is a whole other category of possibilities in which this premise is false. Maybe Jesus never claimed to be Lord. Maybe they only added that part in later. Maybe we've misinterpreted his claim. Maybe Jesus never existed at all. I'd prefer go with the "mistaken" possibility myself, but these new ones are very serious considerations. And I didn't even make an exhaustive list yet. The trilemma argument merely dismisses all these possibilities with hardly an argument. The phrase for this is "begging the question."
In summary, this argument is just abysmal. It is painfully wrong in several distinct ways. It's essentially, "Either we're right or we're wrong. How dare you think we could be wrong! Therefore, we are right." I question the moral character of anyone who poses this as a serious argument.