Martin Gardner's novel The Flight of Peter Fromm is a fascinating portrait of how an intelligent and fundamentally honest person can hold assumptions that he is absolutely incapable of questioning. Peter Fromm's core belief is in the critical importance of having precise answers to questions about the physical nature of God, and especially the question of whether Jesus' body was actually resurrected.
Peter starts out as a Pentecostal fundamentalist who is absolutely certain of the literal inerrancy of the Bible. He sets off to call the intellectual theologians to repentance, and that's where he runs into trouble. With an honest conviction that truth can withstand scrutiny, he delves into all of the different arguments against Bible literalism, and his beliefs gradually change as a result. He becomes fixated on the question of whether Jesus' actual physical remains were truly reanimated. No matter how much heart and effort he puts into it, he can't find a satisfactory answer. This is a problem for him because the one solution he absolutely cannot accept -- the solution that nearly breaks his brain and causes him essentially a nervous breakdown -- is the idea that it's okay to be uncertain about it. Either possible certainty (that the resurrection happened or that it didn't) is far less threatening to his worldview.
The most intriguing point for me is that it doesn't even seem to occur to Peter Fromm that this need for certainty is itself an assumption; one that could potentially be questioned. And, to be honest, it looks like what we're seeing may be the author's own blind spot. He shows us sincere, simple Christians who hardly realize that it's possible for a Christian to doubt the resurrection. He shows us the atheist Unitarian minister who has at least reached a definite conclusion about the resurrection, even if it's not the answer Peter wants to find. Then he shows us the Christians who don't care whether the resurrection really happened or not: because either they're shallow or because they lack integrity. The idea that an honest Christian might have thought seriously about theology and concluded that such questions aren't important? That possibility doesn't exist in this book's universe.
Naturally, it's fun to contrast this book with Duck Egg Blue, another Unitarian-interest book which argues exactly the opposite thesis. One of the main heroes of Duck Egg Blue is a (Christian) Unitarian woman who doesn't care in the slightest what is actually written in the Bible. She just makes up whatever she wants to believe and blithely attributes her statement to Jesus. She thinks that being picky about such things is just another manifestation of closed-minded authoritarianism, and the author Derrick Neill sets up the book's universe to prove her right.
Weirdly, though, the fictional set-up in Duck Egg Blue doesn't precisely contradict the thesis of The Flight of Peter Fromm. The Unitarian in Duck Egg Blue has a value system that's a lot kinder and more tolerant that a fundamentalist's, yet her beliefs come off as being as unexamined and naively simplistic as the beliefs of a Bible literalist, even if the author (perhaps?) intended her spirituality to be deeper and/or more reasonable.
We run into exactly the same conflict in Mormonism, with the Bloggernaclers standing in opposition to both the "True Blue Mormons" and the "exmos" (for a key to this terminology, see here). Wry Catcher wrote a fantastic analysis of this conflict in her post Grayer than thou?.
In a nutshell, the 'nacclers (and other liberal Mormons) congratulate themselves for having a more "nuanced faith" -- one that can withstand disbelieving some of Mormonism's claims without throwing out what's really important. Consequently, they accuse both TBMs and exmos of "black and white thinking," and accuse people who leave the church entirely of "throwing out the baby with the bathwater." But, ultimately, this is less a question of binary thinking than it is a question of which part did you think was the important part? One man's baby is another man's bathwater, so to speak.
I'd also like to point out that religion isn't the only subject where humans hold beliefs that are invisible assumptions that they're not even aware of, hence aren't capable of questioning. I'd give some examples, but of course once you recognize them, they cease to be invisible. My recommendation is to always remain open to the strange and unfamiliar -- stop and think first before fearing and rejecting what you don't understand.
Oh, and what about the book? The Flight of Peter Fromm. Was it good?
I enjoyed it quite a bit. The characters and situation are interesting and (obviously) thought-provoking. The passionate young man of God who's curious, introspective, and open-minded to a point (but ready to clock anyone who pushes him too far...) is a character like no other I've met in literature, and I'm glad to have met him.