The main aim of this book is to convince the reader of Piers Plowman's centrality in any account of the literary and cultural history of the later Middle Ages. It tries to demonstrate how the poem, despite being deeply anchored in a conservative literary, ecclesiastical and social culture, in fact questions that culture in moving towards positions of doubt and dissent, and in reimagining social and religious institutions. The author argues that Langland consistently develops one theme throughout the poem, that of the relations between justice and mercy. In following this theme, certain psychological, institutional, and literary changes become necessary: broadly speaking, the poem moves away from rational to an affective approach to problems; from a hierarchical to a more horizontal sense of ecclesiastical and social institutions; and from authoritarian, closed literary forms to more exploratory and open ended procedures. Simpson takes into account Langland's theology, his idea of the Church as an institution and in a broad sense, his politics. He also tries to show how ecclesiastical and political attachments are written into the formal choices Langland makes. Throughout the poem he considers such questions as what genre is being practised here?, what claims to authority does such a genre make?, what aspect of the self does it appeal to?, what social or ecclesiastical institution is it produced by and does it support? and finally, in what ways are authoritative genres found by Langland to be inadequate. The author aims to address the argument to r eaders who might have no previous experience of medieval culture; a secondary function of the book is therefore to provide brief expositions of any relevant backgrounds which need to be understood before an understanding of Langland's enterprise is possible.