Beginning with a consideration of Malory's ingenious chronology, this study shows that Malory achieved thematic and structural unity by selecting from the great mass of Arthurian legend three narrative strands--the intrigues of Lancelot and Guinevere, the Grail quest, and the feud between the houses of Lot and Pellinore--using these to illustrate a single theme--the rise, flowering, and downfall of an ideal civilization. This selection and use of diverse materials, Charles Moorman asserts, indicates clearly that Malory set to work with a preconceived plan and that he did achieve his purpose, to write the "haole book of Kyng Arthur."