William Blake, posthumously, became a major British Romantic figure, and is often considered the beginning of the Romantic literary movement in England. He presented radical political and esoteric philosophy that later writers of the 19th century developed. Perhaps most significantly, Blake emphasized the idea that poetry should spring from an inspired origin.

The Book of Thel is part of Blake’s prophetic literature. Blake claimed to receive visions from angels; in a letter written to John Flaxman in 1800, Blake said he heard the voices of “Celestial inhabitants.” From these visions, Blake would often rewrite or create Christian and Christian-adjacent mythology. Prophetic literature is a genre that existed for centuries before Blake in many different cultures. In this genre, the poet or writer is merely a conduit for the divine. Prophetic literature became less common after the Enlightenment and the rise of secular thought, but vestiges of it remain in automatic writing and other oracular forms of poetry that exist in modern literature.