What allegory is and how it functions varies hugely throughout its history in the European tradition. One version of allegory sees it as a rhetorical strategy by which a speaker or writer can say one thing but mean another, by means of an extended figuration. A different, theological understanding of it is that allegory consists of events, described in the Bible, which themselves represent other events or spiritual realities, so that the world in a certain sense signifies. Both understandings draw inspiration from Platonist or Neoplatonist philosophical traditions and textual practices. Whatever the justification for such an understanding of hermeneutics, taking a text to have a concealed meaning poses problems. Can such meaning be identified? Who is responsible for that meaning? Consideration of allegory necessitates consideration of texts’ readers, who are variously understood to gain pleasure and understanding through the experience of interpretation or to be faced with a cognitive conundrum according to which the meaning that allegory promises is impossible to find or even to articulate. The work of interpretation is also foregrounded in the commitment in classical, medieval, and modern approaches to allegoresis, the identification of concealed meanings in earlier texts. Such readings find, for example, philosophical truths concealed in the fables of Greek and Roman mythography. While allegorical approaches dominate European 12th-century Scholastic philosophy and literature, as the Middle Ages progress, an Aristotelian literalism overshadows a more Platonist commitment to figuration. Allegory continues in playful narrative poetry, written in the vernacular, in which allegory’s paradoxes and ironies can be enjoyed and indulged, all the while holding out the promise of hidden meanings to committed interpreters. Rejected as stilted and backward by Romantic thinkers, allegory nonetheless persists, both as reclaimed by 20th-century theorists from Walter Benjamin to Northrop Frye and more generally as a way of understanding aesthetic productions whose meaning is not immediately available. Thinking allegorically and thinking about allegory have been at the heart of literary theory and practice in the Western tradition for over two millennia, so that to think about allegory is necessarily to think about what literature means.