Since I've been working my way through the "bad arguments for religion" catalog, and since someone mentioned this particular one in a recent email to me, I thought I'd take a moment and tackle it today. The argument, in a nutshell: Jesus' apostles clearly believed that he was divine, performed miracles, etc. They believed it so strongly that they were willing to be persecuted, tortured, and killed for their beliefs. And they were there! What they believed must have been true!
First of all, this argument is assuming one of the main things it's trying to prove: namely, that the New Testament is a reliable and accurate source of information about the events that happened in that time and place. Which it's clearly not. The New Testament is shot through with factual errors and internal contradictions; and it was written decades after the events it supposedly describes, by people with a passionate vested interest not only in believing these events but in persuading others about them. A reliable source this is not.
But for the sake of argument, let's concede that point for the moment. Let's pretend that the New Testament is a reliable and accurate source of information, at least about the basic historical events if not about the supernatural stuff. Let's say, for the sake of argument, that there was a historical Jesus, that he had apostles who believed in his miracles and his divinity, and that those apostles were willing to sacrifice their lives for this belief.
How is that an argument for their belief being true?
People believe all sorts of things that aren't true. People believe that President Obama isn't a U.S. citizen, that the moon landing was a hoax, that Uri Geller can bend spoons with his mind, that they personally have been kidnapped by space aliens. People believe these things with absolute sincerity and passionate conviction.
But the fact that they're really, really convinced that these things are true is not evidence that they are actually true. The human mind plays weird tricks on us. (Read Michael Shermer's Why People Believe Weird Things for a good discussion of this phenomenon.) And the more we've committed ourselves to a belief, the more deeply we rationalize that belief and convince ourselves that it's true.
To the point where some people will even die for their beliefs.
Whenever someone makes the "conviction of the Apostles" argument, I want to scream at them: What about the followers of the Heaven's Gate cult? What about the followers of Jim Jones? What about suicide bombers and the 9/11 terrorists? They were convinced of their beliefs, too. Convinced enough to die for their beliefs. Does that make those beliefs true? Does that mean that there really are 72 virgins awaiting any Muslim who dies to defend his faith? That the Hale-Bopp comet really had a spaceship following it to take the Heaven's Gate followers to the Next Level, as long as they were wearing Nike sneakers? That Jim Jones really was God? (Yes, I know many of the Jonestown victims were murdered and not suicides -- but at least some of them truly believed that Jim Jones was God and that they should kill themselves on his say-so.)
The argument from conviction is just a slightly tweaked version of the argument from popularity. Instead of saying, "Lots of other people believe this, therefore it must be true," it says, "Some other people believe this a lot, therefore it must be true." Which still makes for a truly lousy argument.
I think there's an element of guilt tripping and emotional blackmail involved here as well. It's like, "These people died for their beliefs -- are you going to make their sacrifice be in vain? Or worse -- are you calling them liars?" And there's a circularity to it, too. People will readily say that the Heaven's Gate cultists were delusional to sacrifice themselves for such an obviously nutty belief... but the Apostles' sacrifice, that we have to take seriously. Why? Because the story of Jesus' divinity and miracles isn't absurd. And why do we think Jesus' divinity isn't absurd? Because the Apostles said it was true.
I've said this before, and I'll say it again: The only "evidence" we have of God or the supernatural comes from the inside of people's heads. There is not one scrap of good, carefully- collected external evidence supporting the God hypothesis. It's all sacred texts, or "my parents taught me this," or "I feel it in my heart." Or, "The Apostles believed this, and they died for their beliefs -- and nobody would sacrifice themselves for a belief that wasn't true."
Just like the Heaven's Gate believers.