James Blish considered Black Easter and The Day After Judgment to be one narrative unit. As one unit, they are part of the After Such Knowledge trilogy (1991), which also includes A Case of Conscience (1958) and Doctor Mirabilis (1964). The three parts of the trilogy are connected more by theme than by plot. Doctor Mirabilis is a historical novel about thirteenth century scholar Roger Bacon; A Case of Conscience is a science-fiction novel about an alien society that seems to be free of sin. All the books deal with theological themes of innocence, sin, knowledge, and power.
In Black Easter and The Day After Judgment, traditional European ceremonial magic actually works. This magic requires summoning spirits or demons. Both “white” (good) magic and “black” (evil) magic exist. White magicians have limited power and call on demi-urges. Black magicians have extensive power obtained through the use of demons. A covenant governs the relationship between white magic and black magic. Blish is vague about the precise terms of the covenant, but it allows a priest to be an observer at the summoning of demons as long as he does not interfere with the ceremony. Blish’s “Author’s Note” explains that he has tried to present magic as it would be if it were real, using historical sources. Blish also cautions that he has not presented enough information for readers to attempt...
(The entire section is 590 words.)