Critics have long pondered William Blake's relationship to his literary predecessors. As both a visual and verbal artist, Blake had a bulk of precedence and tradition at his disposal. Many scholars focus on Blake's relationship to Christian sources, most notably biblical and Miltonic narratives, especially with regards to his epic poem Milton. Those critics often read Milton as Blake's attempt to correct the century-and-a-half's worth of misreadings that had accumulated between the writings of Paradise Lost and Blake's own epic. However, my thesis argues that Blake's use of his sources is much more multi-faceted than the one-to-one relationship between Milton and Blake that this reading implies. By bringing the vocabulary of adaptation theory into Blake studies, I argue that Blake's adaptive method becomes a means for him to assert his own cultural capital and purge his network of sources of their impurities. From Paradise Lost, Blake takes the fall plot and the character Sin-Leutha, correcting and updating Milton to better suit Blake's personal mythology and vision for England. Blake turns an even more critical adaptive eye to Homer and Virgil, as he transforms the shields of Achilles and Aeneas to the garment of the Shadowy Female, criticizes the classical glorification of war, and offers a corrective through a purification of that garment. My third chapter revisits the motifs of the fall and weaving and views them through the lens of Norse mythology to show that Blake's adaptive method is multiplicative in its design. This far-reaching and cleansing process of adaptation becomes Blake's means of forging a national myth of England as a mythic paradise, joining Albion with his emanation Jerusalem.