Most Miltonists have treated Paradise Lost as a static design, emphasizing its balance, but McMahon stresses its movement. He explores the differences between the poem's earlier and later books, linking them to the Bard's growth as a poet. The first half of Paradise Lost swells with matter and manner of the classical epic, reflecting, McMahon says, the Bard's aspiration to be a visionary poet in the grand style.

A shift occurs in Book VII, however, and by Books XI and XII the Bard composes in a simpler fashion, singing a narrative exegesis of the Bible and exhibiting concern for his audience's edification rather than his own glorification.

The later books of the poem, therefore, are presented as morally better than the earlier, according to McMahon. Even more, Milton understood them to be aesthetically better. The change that the Bard and his poetry undergo illustrates Milton's attempt to reform the taste of his readers, to lead them from the pleasures of the grand style to a more austere and biblical poetry.