For many writers, the theme of a novel is the driving force of the book during its creation. Even if the author doesn't consciously identify an intended theme, the creative process is directed by at least one controlling idea — a concept or principle or belief or purpose significant to the author. The theme — often several themes — guides the author by controlling where the story goes, what the characters do, what mood is portrayed, what style evolves, and what emotional effects the story will create in the reader.
Igbo Society Complexity
From Achebe's own statements, we know that one of his themes is the complexity of Igbo society before the arrival of the Europeans. To support this theme, he includes detailed descriptions of the justice codes and the trial process, the social and family rituals, the marriage customs, food production and preparation processes, the process of shared leadership for the community, religious beliefs and practices, and the opportunities for virtually every man to climb the clan's ladder of success through his own efforts. The book may have been written more simply as a study of Okonkwo's deterioration in character in an increasingly unsympathetic and incompatible environment, but consider what would have been lost had Achebe not emphasized the theme of the complex and dynamic qualities of the Igbo in Umuofia.
Clash of Cultures
Against Achebe's theme of Igbo cultural complexity is his theme of the clash of cultures. This collision of cultures occurs at the individual and societal levels, and the cultural misunderstanding cuts both ways: Just as the uncompromising Reverend Smith views Africans as "heathens," the Igbo initially criticize the Christians and the missionaries as "foolish." For Achebe, the Africans' misperceptions of themselves and of Europeans need realignment as much as do the misperceptions of Africans by the West. Writing as an African who had been "Europeanized," Achebe wrote Things Fall Apart as...