William Blake's ideas in The Marriage of Heaven and Hell derive from a wide range of sources. From his childhood on, he claimed to have mystical or spiritual visions that formed the source of his poetry and art. Several other thinkers also influenced his work.
The strongest influence is the Christian Bible. Although his interpretations are often idiosyncratic, and he adds his own personal ideas, history, and characters to the Biblical substrate, his work constantly engages Biblical themes, albeit critically.
Another major influence was a work called Heaven and Hell by the Swedish mystic Emanuel Swedenborg; especially relevant is the way Swedenborg gave prominence to angels, demons, and other spirits, something absent from the Enlightenment Protestantism of England in Blake's period. Blake was strongly influenced by Swedenborg and his English followers, but moved away from Swedenborg's influence before writing this book.
Two strong literary influences are Dante and Milton, poets who wrote long epic poems on Biblical themes. Blake actually wrote a long poem about Milton, and was influenced by (his own reading of) Milton's vision of Satan.
Finally, Blake was personally acquainted with the early Romantics, and considered a member of the Romantic movement.
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