In the fourteenth century Geoffrey Chaucer, who served three kings as a customs official and special envoy, virtually invented English poetry. He did so by wedding the language of common speech to metrical verse, creating a medium that could accommodate tales of courtly romance, bawdy fabliaux, astute psychological portraiture, dramatic monologues, moral allegories, and its author's astonishing learning in fields from philosophy to medicine and astrology. Chaucer's accomplishment is unequalled by any poet before Shakespeare and--in The Canterbury Tales and Troilus and...