William J. Long,
Outlines of English and American Literature
“ In Prometheus Unbound Shelley uses the old myth of the Titan who rebelled against the tyranny of the gods, and who was punished by being chained to a rock. [Footnote: The original tragedy of Prometheus Bound was written by Æschylus, a famous old Greek dramatist. The same poet wrote also Prometheus Unbound, but the latter drama has been lost. Shelley borrowed the idea of his poem from this lost drama.] In this poem Prometheus (man) is represented as being tortured by Jove (law or custom) until he is released by Demogorgon (progress or necessity) ”
