An author might start a novel from any of several vantage points - from the germ of the plot, or from a character, or from the theme, or from some combination of these.
Let's take an example. Perhaps you, an author, think it would be interesting to write a novel about revenge. You think revenge is sweet, but you also think it could lead to unforeseen consequences that are not so sweet. Perhaps that is how Alexandre Dumas began his creation of The Count of Monte Cristo, or Victor Hugo began The King Amuses Himself (which became Rigoletto), or Sem Benelli The Jester's Supper (or many other works which treat this same idea). So this approach starts with a theme.
But maybe it was the other way around - perhaps Dumas started very concretely, perhaps he imagined a hero, physically striking, with dark hair and pale skin, tall, forbidding, sophisticated who was a kind of avenging angel bringing justice to wrongdoers. What could have produced such a person? Well, maybe he was himself the victim of the wrongs these people had perpetrated. Then, by following out the implications of this idea, Dumas created the story. The working out of the theme followed after a very specific initial image.
Or again, maybe Dumas saw a real life young man who was bright and talented, and who was deprived unfairly of some position. Then, perhaps he said, "Let's make it worse: deprive him of his family, and his beautiful bride just at the moment when he should be coming into possession of everything. He is cast from a position above to a terrible situation below. Now, how can I show him regaining all that he lost?" (It may be that this is the kind of beginning that Conrad refers to in the "Author's Note" to Lord Jim)
So an author might take some small kernel and grow an oak from it. Or he might start with an image of the oak, and then work backwards to its acorn-ish beginning.
I started with this idea: two brothers, who are racial half-brothers. One is a racist and the other an individualist. What would happen given this start? This kernel I imagined all at once, and then I saw that it would make for a dramatic way to illuminate the themes of individualism and racism. But it immediately struck me that it would be better, would be much more dramatic, if they both loved the same woman. So that was it.
But this immediately leads to a problem. It is unlikely that a woman who was loved by the hero-brother would also be equally loved by the racist brother. And just as unlikely that she would return the love of both men. So here was a conundrum: how to develop these three persons so that the dramatic conflict was there, yet resolvable plausibly given their three different characters. You will have to read the novel, of course, to see how I solved it.
In writing the novel, I had to struggle with the following dilemma: how to present race as a major thematic element without promoting Race. How to show racial and ethnic features, attributes, customs without making them important.
For example, many, many books have been written about this race or that, this ethnic group or that. (A tiny sample: Invisible Man, The House Behind the Cedars, Roots, Giants in the Earth, My Antonia. In so doing, they perforce made race important. Some of these authors explicitly believed that race and/or ethnicity are important. Some were trying to say that it should not be important. But in writing a novel about race you necessarily make it important within the pages of the novel.
And you especially make one race or ethnic group important, whether that is black, or white, or Norwegian, or Vietnamese, or whatever.
Now I crucially did not want the reader saying, “Oh, this book is about whites versus blacks,” or “about Jews,” “about black people,” or “about Orientals,” or about any one racial or ethnic group of people. First – because that would contradict the theme of the book which is that the individual is all that matters and that race does not matter at all. Second – If a specific race or ethnic group were featured, then readers might identify with or distance themselves from the characters because of their own race or ethnicity, whereas I wanted the reader to universalize what I had to say – to say to himself “This could be any race,” “This could be any immigrant community,” “This could be any individual human being,” -- and especially, "This could be me".
In short, I had to create not Everyman but rather, Every-race.
And so, during the writing, I kept ever in front of my mind to keep the reader off balance in regard to just what was the racial or ethnic identity of Chugrans. I built into their history, their physical features, their customs, their names, and their customs an array of characteristics culled from many different peoples. Even the location of Chugrana was left mysterious and somewhat ambiguous. It is just “over there somewhere.” (As Conrad, in Nostromo, created a fictitious country called Costaguana which was just -- somewhere in South America.)
This created a special problem in character description. The reader will have to be his own judge as to how effective I was. For my part, I am satisfied that I was able to endow the of characters with full individuality, while leaving some physical attributes elliptical or unstated.
In Oscar Wilde's The Importance of Being Earnest, Miss Prism admonishes her ward Cecily: "Do not speak slightingly of the three volume novel." Certainly I never set out to write such. I first conceived only the essential story within Part Three. The rest I envisioned only as background. As I began to flesh out that main story, I began to see that more "background" was necessary. The project contained within it a more ambitious development than I knew.
So, when I began to create that background, I found it necessary to explain the deepest sources of the characters of the two boys. Further, for reasons having to do with how they developed later, I decided that I had to force a separation from their parents. Thus, the history and life of Zaq and Chugrana became, likewise, more important than I had first planned.
So now I had Part One and Part Three: evidently I would have to show how one got from A to C by creating B. So, Part Two, which in my mind had only been Braq's time at the Atelier Derosch, grew from this small glimmer into the major period of character development for the two boys, the time when their characters were truly set.
This isn't an apology - from my earliest days I loved long novels - but rather an explanation. I doubt that any author with an ambitious theme knows ahead of time whether he can concretize that theme properly in two hundred pages or one thousand.