The English poet and artist William Blake (1757-1827) was uncommonly aware of the evils of slavery in his time, having illustrated Narrative of a Five Year's Expedition against the Revolted Negroes of Surinam (1791), John Stedman's firsthand account of the brutal suppression of a slave revolt in South America. But for Blake, the interest was not only in physical but mental enslavement. The ubiquity of "mind-forg'd manacles" (as he put it in...