William Langland was, in an entirely different way, as great a poet as his contemporary Geoffrey Chaucer. Langland's ""Piers Plowman"", his life's work, most often sounds like an odd mixture of dream-vision, satire, sermon, and allegory, as if its purpose were aggressively didactic. Some critics explicate the poem as a coherent system of doctrine. Others deny system, preferring to think of the poem as recording a number of inconclusive stories into some of the thorniest thickets of medieval philosophy and theology. This study treats the poem as the work of a 14th-century intellectual - that is, as the work of a litteratus, one obsessed with written texts, who interprets all human experience on the model of textual interpretation. But instead of providing a theory of interpretation, Langland shows what happens when incommensurable interpretive systems collide. The dreamer in the poem learns that the intellectual's lust for self-justification on the model of textual argument is futile and self-destructive, and yet that the intellectual must approach God, if at all, through texts. Literacy turns out for the intellectual to be itself instrumental like sin: an understanding of the wrongness of wanting to master texts in order to justify oneself provides the stimulus for a necessary refocusing of one's life. William Elford Rogers provides a reading of the poem that addresses most of the central issues current in Langland criticism. The book should be of interest to scholars of Langland and of 14th-century literature, to medievalists, and to scholars of any discipline interested in the reflections of a medieval intellectual on the implications of widespread vernacular literacy.