The importance of the theme of the double in Borges's work has long been recognised. His short piece entitled ‘El doble’ (The Double) within El libro de los Seres Imaginarios (The Book of Imaginary Beings) describes this internationally widespread concept. He starts by referring to mirrors, water, and twins, friendship, and knowing oneself. Then he mentions the German doppelgänger; and the Scottish ‘fetch’, which comes to fetch men to lead them to their deaths. ‘Encontrarse consigo mismo es, por consiguiente, ominoso.’ (To meet yourself is, consequently, ominous.) He refers to various writers, including Stevenson and Poe; he says the Double is the hero's conscience in Poe's story ‘William Wilson’. Many of Borges's fictions have characters whose double is also present. In ‘La muerte y la brújula’ the reasoner and detective Lönnrot is trapped by the criminal he is trying to catch, his own double the Dandy Scharlach. In the story ‘Los teólogos’, Juan de Panonia and his accuser Aureliano are also doubles; these rival theologians in paradise become one person in the eyes of God. In ‘La forma de la espada’, the Irishman called ‘El Inglés’ is actually Moon, the betrayer; the hero becomes the traitor, but they both bear the same scar. He is a reflection of himself, his own double. In ‘Historia del guerrero y de la cautiva’ the two stories reflect each other, and all the main characters are doubles. Borges's grandmother commented on her destiny as an English woman exiled to the end of the earth; and Droctulft, we are told, was not a traitor, but an enlightened convert. All the main characters have been uprooted from their homeland and culture; they are all exiles.

Perhaps Borges's most famous piece about the double is about himself and his own alter ego, ‘Borges y yo’, published in the collection El hacedor. There are two protagonists: ‘Yo’ the private man, the narrator; and ‘Borges’, the public man, the Other. In this description of their daily life, the only literary character mentioned is Stevenson, the author of Jekyll and Hyde, the literary master of the topic of the double. ‘Me gustan los relojes de arena, los mapas, la tipografía del siglo XVIII, las etimologías, el sabor del café y la prosa de Stevenson.’