King Arthur has been depicted throughout history as a pagan leader, a Christian leader, and an irreligious leader who sought to bridge the divide between pagans and Christians to rule them in one peaceful kingdom. John Steinbeck's interpretation, a modernized translation of Thomas Malory's Le Morte d'Arthur, would accept the thread of Arthur as a Christian king, though the themes of Christianity are more allegorical than spoken. (Malory's "Joseph of Arimithea" tale is important for both Christian context and as a medieval transition from the interpretation of Arthur as a pagan/irreligious ruler to a god-fearing one.)
While Arthur appears an obedient servant, insisting upon Christian behavior in his knights, he constantly questions what Merlin tells him is his destiny. His struggle against reality can be interpreted as man's struggle against his own limited knowledge of God's grace, plan, and the universe. As in Malory's writing, Lancelot stands in as a dual figure, both Peter and Judas, to Arthur's Jesus.
Arthur's faith in God is tested through the grail quests that leave his kingdom depleted. His knights return without any success, and the land decays because of their unworthiness. Arthur wants to give up the questing, but Merlin convinces him that the grail quest is God's plan for him and the knights. The fruitless grail campaigns are an example of faith over reason; in spite of worldly obstacles, and even through great suffering, faith is more important than results.