Every character (except perhaps the walk-ons) must have an incentive for what he does. He must have a motivation that will drive him to reach certain goals he's set for himself. Like characterization, his motivation must be consistent throughout the book. It must be believable to the reader and strong enough to carry the story to the end.
Motivations tell you what type of person your character is, or has to be in order for the book to work. Motivation and characterization work hand in hand until they mesh together into what your plot will be.
As an example of how integral motivation and characterization are, consider the two main characters in Larry McMurtry's Lonesome Dove, the 1985 Pulitzer Prize winner. Woodrow Call is a man driven to action. He's a leader of men and has little tolerance for laziness or weakness in anybody, even himself. On the other hand, his best friend, Augustus McCrae, is a man who, like Call, can hold his own in an Indian battle and who loves adventure. But McCrae is also a man inclined to need a little nudge to get going unless it's something he wants to do. He likes his whiskey and his women--two things Call scorns. Contrary to Call, McCrae doesn't believe in working too hard, and he definitely doesn't believe in working continually.
The fact that Call is a driven man sets the book into motion. He wants to head a herd of cattle north to Montana. He's tired of the sameness of the last ten years in the little border town of Lonesome Dove. Maybe everybody is tired of the sameness, but he's the one who takes the action. Because of his personality and the fact that he is an ex-Texas Ranger with diverse experience, the reader never doubts that he can accomplish the feat. If McCrae had spearheaded the cattle drive north, he would have needed a different personality and motivation in order for it to be truly believable.
In this book every person has his own goals, even if some of the goals don't seem obvious at first. And each person has his own motivations in order to reach those goals. Who the characters are and what they want from life dictates their separate ends. They either go along with Call or they rebel, or like Lorena--the good-hearted whore--they use the drive to obtain something they want. Their motivations are the story. In this book we get a good look at the West and at what cattle drives were all about, but the people and their motivations are the actual story.*
Next week: WHAT'S AT STAKE?
COPYRIGHTED MATERIAL: *From my 1992 RWR article: "The Outline: Your Blueprint for a Structurally Sound Plot."