Psst! Wanna hear a secret? The people in most stories aren't really humans -- they're robots! Real people are quite accidental, the result of a random jumbling of genes and a chaotic life. But story people are made to order to do a specific job. In other words, robots! I can hear some of you pooh-poohing this notion, but it's not my idea. It goes back twenty-five hundred years to the classical playwrights. In Greek tragedy, the main character was always specifically designed to fit the particular plot. Indeed, each protagonist was constructed with an intrinsic hamartia, or tragic flaw, keyed directly to the story's theme. These days, writers have more latitude in narrative forms, but we still try to construct characters appropriate to a given tale. 

Consider, for instance, Terence M. Green's Barking Dogs. The book posits the invention of infallible portable lie detectors. Of all the people in the world, Green chooses to give such a device to Mitch Helwig, a Toronto cop. Why that choice? Well, no one other than a cop deals so directly with questions of truth, and no one but a cop is so frustrated by the perversion of that truth, seeing guilty people he's arrested get off on technicalities. Armed with his lie detector, Mitch goes on a vigilante spree, ascertaining as soon as he nabs someone whether that person is guilty, and, if so, executing them. Green knew he had to find the character who could best dramatize his premise. 

Frederik Pohl knew the same thing when he wrote Gateway. Its premise is simple: near a black hole, the passage of time slows to a stop. To make this dramatic, Pohl came up with Robinette Broadhead, a man who had done something horrible to people he'd left behind near a black hole. The story is told through psychoanalytic sessions: Robinette can't get over his guilt because no matter how many years pass for him, it's always that one terrible moment of betrayal for those he's left behind. The novel works spectacularly -- in fact, I'd go so far as to say it's the finest science-fiction novel ever written. Others liked the book, too -- and Pohl was pressured for a sequel. But the second book, Beyond the Blue Event Horizon, fell flat on its face. Why? Because Pohl had to shoehorn the character he'd built for a very specific job into a different story. Robinette, absolutely perfect for Gateway, was a fish out of water in the follow-up story about the discovery of a human child on an ancient alien space station. 

Clearly, your character must fit your premise -- but it's also important that you not make the fit too comfortable. Everybody knows Steve Austin, the fictional test pilot who lost an arm and both legs in an aircraft crash and was rebuilt with super parts so that he could undertake secret missions. Austin first appeared in Cyborg, a mediocre novel by Martin Caidin, and was played by Lee Majors in the wonderful, Hugo-nominated movie The Six Million Dollar Man. 

Why was the novel just so-so but the movie glorious? Simple. In the novel, Steve Austin was a colonel in the United States Air Force. When he was asked to undertake his first mission as the bionic man, he told his new secret-agent bosses, "You have a job to do. It's serious, in many ways it's dirty, in some ways it stinks, but having worn the blue suit [an Air Force uniform] for a long time, I understand and even appreciate what you do. You will receive my absolute cooperation." 

Ho hum. Screenwriter Henri Simoun saw that Caidin had missed the essential conflict. For the movie version, he changed Colonel Austin to Mister Austin, one of six civilians in the U.S. astronaut program. Simoun's Austin fights those who are trying to make him an obedient little robot every step of the way -- making for much better drama. (When The Six Million Dollar Man became a TV series, the producers went back to Austin being an Air Force officer, and the show degenerated into mindless adventure.) 

I almost made the same mistake Caidin did in my novel The Terminal Experiment, which is about the discovery of scientific evidence for the existence of the soul. My first thought had been to have a protagonist who had undergone a metaphysical bright-light-and-tunnel near-death experience. But that would have been absolutely the wrong choice. A person with that background would be predisposed to believe in the existence of the soul, accepting any proof too readily. No, what was called for was a skeptic -- someone who had stumbled on the existence of the soul while looking for something else, and who would be bothered by the discovery. The lesson is simple: your main character should illuminate the fundamental conflict suggested by your premise. And, of course, that means that you shouldn't start with a character and then go looking about for a story; it's a lot easier to do it the other way round. 

First, come up with your premise (for instance, "I want to write about a telepathic alien who can read subconscious instead of conscious thoughts"). Then you ask yourself who could most clearly dramatize the issues arising from that premise ("There's this guy, see, who's been suppressing terrible memories of the suicide of his wife"). 

After that, head for your keyboard and build the character to your specifications, for that one specific job. (In this case, the story has already been done brilliantly; it's Solaris by Stanislaw Lem.) Of course, you have to add subtleties and quirks to give your character depth, but if you do it right, only you will ever know that underneath the real-looking skin, your hero is actually a made-to-measure robot . . .