History most directly differs from fiction because it has an external referent, the real past. Writers of fictional literature, however, live in the real past or present and transform their experiences and thoughts into narrative. Though in a logical sense, one can argue that each fictional creation is an entire possible world, these possible worlds have varying degrees of similarity to the real world and its real past. For Hans Vaihinger, "fictionalism" enables the separation of mental constructs from correspondence to or verification by the facts of the real world. Fictionalism as a concept has become very important in recent analytical debates about the metaphysics of possible worlds, and I argue that it enables us to understand how a faculty of mind optimized for understanding the world as a whole (narrative) compensates for the partial experience of the writer. This tension between optimality and necessarily limited experience is manifest both in the process of narrative creation and narrative comprehension.