My dissertation, The Rational Double, reveals a literary tradition of the double that has been obscured by the prominence of psychoanalytic investigations of the theme. Using concepts from narratology and the analytic philosophy of persons, I define the thematic field of the double, emphasizing the diversity of its kinds. I show how the Freudian conflation of two distinct classes of the theme, the paranormal and rational traditions of the double, has resulted in literary historical confusions that I then redress. In my first chapter, I historicize the rational double, in its several forms, as it emerges in an Anglo-American context, showing how modern iterations of the theme, in Locke and Dryden, and later in Pope, Swift, and Adam Smith, among others, become conceptual tools adapted to understand newly emergent concepts of persons, property, and personal identity. Having established the structural forms and thematic resonances of the double as they evolved in the long eighteenth-century, I trace in the two remaining chapters the persistence of these same forms of the double in nineteenth-century Anglo-American fiction and philosophy.