These thumbnail interpretations from the book Film Noir by Alain Silver and James Ursini, are compelling renditions of the two essential themes of film noir:
The Haunted Past… In the noir world both past and present are inextricably bound… One cannot escape one’s past… And only in confronting it can the noir protagonist hope for some kind of redemption, even if it is at the end of a gun.
The Fatalistic Nightmare. The noir world revolves around causality. Events are linked… and lead inevitably to a heavily foreshadowed conclusion. It is a deterministic universe in which psychology… and even the structures of society… can ultimately override whatever good intentions and high hopes the main characters may have.