Why do people believe with such intensity in things that have no direct bearing on their lives at all? Why, for example, would people kill each other because they disagree about the nature of the afterlife?
One answer is that the question of the true nature of the afterlife is important, and I’m willing to agree with that. But it’s still, shall we say, abstract. And someone else’s misconception about it doesn’t have much direct impact on us. So why do we get so upset about questions like this? And isn’t it a big disadvantage for us as a species if we get so irrationally upset?
Another answer is that we don’t actually get upset about questions like this; we get upset about other, much more material and rational questions – wealth, power and so on – and mask them in the language of ideals and abstractions. There’s certainly some truth to this too.
But that answer makes the assertion of our ideals seem like a charade, and a pretty transparent one at that. I think the capacity to believe, sincerely and even fanatically, in ideals is not a charade and not entirely a weakness. If people need to be part of groups to survive, then they need something to make those groups hold together, and hold together even when rational temptations might cause them to dissolve. Holding ardent, shared beliefs is a group-promoting behavior.
So it seems to me that over human history the capacity to become deeply attached to ideals was probably a useful survival strategy. Even martyrdom in the name of those ideals was probably useful – not to the individual giving his or her life, of course, but to the group of which the martyr was a part.
Certainly it might be argued that what was useful to our ancestors, living on the border of the state of nature, is now just dangerous for us. Fanaticism is dangerous for us – not only for the innocent victims of the fanatics’ zeal but even for the fanatics and their causes. To be clear, I'm not in favor of fanaticism at all. But still I fear we have not moved so far from the state of nature that group solidarity, which ardent belief fuels, has lost its value.