One of the better pieces of creative advice I've received is "Look for the cracks in things." Leonard Cohen has a couplet along those lines: there's a crack in everything, that's how the light gets in. But the right way to apply that advice eluded me for a long time.
A major element of Flight of the Vajra is the Old Way, a kind of techno-renunciationist spiritual movement of the far future. The people who follow it are not wholly against technology, but against specific things they feel degrade the long-term meaning of both life and death. E.g., being able to back up one's mind and restore it into any number of bodies, which to them is grotesque because it provides you with one way to avoid ever confronting the aging of the spirit within. (Note that I'm not saying I advocate or support such ideas; I just wanted to dramatize the conflicts in and around them.)
Not long after I'd drafted the whole concept of the Old Way and populated the story with it, I hit a wall. Eventually, I told myself, such a thing is going to be tested and found wanting. If such a regressive belief can't, for instance, provide genuine comfort for those who lose their children, then it's going to fail in the long run. In time, people will leave it behind.
I was on the verge of scrapping everything and starting over when something else hit me: That very potential failure deserved to be the subject of the story. In other words, I shouldn't be writing about how this synthetic system of faith would provide comfort to people when I knew perfectly well it wasn't likely to do that in the bigger picture; I should be writing about the fact that there were instance when it was clearly not able to do that, and make that into the substance of my story. And so off I went.
After I was done, I found I had plucked yet another bit of fruit off that particular tree of wisdom. The "easy" handling of the material — the one where the religion is essentially some static piece of story backdrop thrown in for the sake of exotic color, one where its tenets as an actual belief system are never tested, found wanting, put into conflict in terms other than as a plot convenience, etc. -- amounted to nothing more than a kind of wish-fulfillment. The fact that I had the impulse to make the story about something fundamentally less challenging than what I ended up with meant that I had been tempted into writing what, on the whole, would amount to a piece of wish-fulfillment.
But I knew full well I couldn't do that. Too many other SF (and fantasy) books exist that suffer from that flaw. Not to say Vajra has no flaws — hell, we could create a veritable Bingo scorecard full of 'em — but that if there was one mistake I knew I could not afford to make when constructing this story about this idea, this was it. And if there is any one choice I made with that story that I can say with complete confidence was the right one, this too was it.
Not because it was easy, but because it was hard.