In formula fiction, human emotions and motives are usually direct, unmixed, and dramatic. In more sophisticated works, as in real life, the reasons behind someone's actions may be more complex.

People may act from mixed motives, or be driven by a jumble of conflicting emotions. Mixed motives can affect the plot, the theme, even the tone of a novel.

In some novels, the characters' true motives and feelings may be left up to the reader to interpret. In Le Divorce, Diane Johnson has characters who almost always act from mixed motives, and some, like Roxy, exhibit emotions that veer back and forth between extremes. The mixed motives are visible—at least to the reader, and increasingly to the narrator as the story goes along. Yet they have little impact on the plot. For example, Edgar's outrage about the Bosnian war is probably real; at the same time...