This introductory chapter traces the origin of the poetics of friendship to Aristotle’s Nicomachean Ethics and, by extension, Cicero’s De amicitia. Aristotle’s definition of the perfect friend in static categorical terms presents significant challenges to narrativization, that is, to a mode of literary expression based in conflict and change. Following Ullrich Langer, the chapter explores how Aristotle’s largely static categorical framework is filtered through the discourse of spiritual friendship in the Middle Ages, exposing the key problem of the perfect friend’s ultimate unknowability. Alternatively, following Cicero’s more fluid dialogical exploration of the problem of friendship, the chapter traces a second trajectory for a poetics of friendship that draws on Kathy Eden and Nancy Struever’s work on the more recognizably modern notion of intimacy. Taken together, these two genealogies provide the foundation for an evolving poetics of friendship in the narrative prose and dramatic works of early modern Spain.