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.