This is the first monograph to provide a comprehensive interpretation of the Decameron's response to classical and medieval didactic traditions. Olivia Holmes unearths the rich variety of Boccaccio's sources, ranging across Aesopic fables, narrative collections of Islamicate origin, sermon-stories and saints' lives, and compilations of historical anecdotes. Examining the Decameron's sceptical and sexually permissive contents in relation to medieval notions of narrative exemplarity, the study also considers how they intersect with current critical assertions of fiction's power to develop empathy and emotional intelligence. Holmes argues that Boccaccio provides readers with the opportunity to exercise both what the ancients called 'Ethics,' and our contemporaries call 'Theory of Mind.' This account of a vast tradition of tale collections and its provocative analysis of their workings will appeal to scholars of Italian literature and medieval studies, as well as to readers interested in evolutionary understandings of storytelling.