Using the idea of a "flexible design," John Pierce examines the ways in which Blake's mythology and his poem possess a flexibility that allows for significant change to characters, symbols, and poetic techniques within a previously constructed framework. Pierce traces how, in the process of revision, Blake experimented with characterization, increased the importance of Christian symbolism, and developed a mode of narrative presentation controlled less by chronological sequence than by the use of thematic juxtaposition and typology.