This work examines the psychomachia, or battle of the soul, as it occurs in the 14th century poem, Sir Gawain and the Green Knight. Based on an analysis of the Gawain-poet’s earlier work, as well as contemporary analogs in chivalric manuals, Arthurian romances and mystical literature such as The Cloud of Unknowing, it argues that Sir Gawain’s quest into the Otherworld is a tragedy of limited, human perception pitted against a mysterious Infinite that deigns to destroy the mortal protagonist’s delusion of knowing. The fault of Sir Gawain, therefore, occurs after his ordeal at the chopping block, arising from excessive pride in his own chivalric self-conception. As such, the Gawain poet’s final work is a masterful culmination to his life-long exploration of the themes of purity, confession, and unclouded spiritual perception.