Self-deception is a problematic phenomenon because it seems so deeply irrational. Previous philosophical accounts have not succeeded in making clear the way in which it is a "failure of reason." The present author argues that self-deception is a privative phenomenon, i.e. a deviation from immanent norms, as well an ethical phenomenon. According to this approach, self-deception is motivated epistemic caprice that is tempting when we see our idea of a good life threatened.