The Introduction summarizes the book’s arguments and expands on the critical tradition of allegory theory that underpins the book. It discusses the five conflictual allegorical structures that will be the focus of the book as well as their appearance, substantially remodelled, in Piers Plowman. These are the paradiastolic ‘hypocritical figure’ (vices and virtues made to look respectively like ‘adjacent’ virtues and vices), personification debate, violent language and apophasis, narratives of bodily decline associated with age and sin, and grail romance. Through the study of these five allegorical structures, the book will pursue a larger thesis about the fundamentally disruptive nature of allegory, a form of writing that comes into being wherever two or more contrasting languages are brought into a relationship or used to comment on each other. Drawing on a number major theorists of allegory, the Introduction reaffirms that the characteristic modes of the most thoroughgoing and serious allegorical narrative in the Middle Ages are dialectical, conflictual, episodic, hypotactic, ironizing, and linguistically diverse. The Introduction further argues that such forms of strategic dissonance and the questioning of perceived continuities may be particularly common in religious allegory, with its tendency towards critique, iconoclasm and apophasis.