What is the theme in The Human Stain by Philip Roth?

While Roth's treatments of the human condition often argue that life makes no sense (see, for example American Pastoral in which Seymour "Swede" Levov, his paragon of decency and convention, learns just that lesson), The Human Stain argues a profound question, one that poets have been examining for thousands of years. How do you know who you are, the Sophoclean question? And what are the consequences of either not knowing or of denying one's identity? At the heart of this thematic question is the related one of knowing and recognizing one's parents.