Moncure Daniel Conway embarks on an exhaustive etymological and historical investigation into how human societies transformed primitive nature worship into structured demonology. The central problem posed by the author is the psychological and theological mechanism through which ancient beneficent deities, such as the personifications of the sun, storms, and the elements, were progressively degraded into malevolent demons and devils as religious systems clashed and evolved. The argument develops by examining how the dualistic worldview split the primitive pantheon into hostile camps of good and evil powers, reflecting humanity's endless struggle against hunger, extreme heat and cold, disease, and death. Conway traces the genealogy of evil across various cultures, demonstrating how foreign gods were conquered, demonized, and integrated into theological hierarchies as the abgott, or ex-god.
Main storylines and recurring motifs involve the transition of nature forces into personified monsters, such as the eclipse devourers of India, the freezing hells of northern sagas, and the serpent and dragon myths representing obstructions and time. The text meticulously categorizes demons by their functional origins, separating the hungry devourers and elemental spirits from the later spiritual conception of a purely malignant devil. The argument culminates in showing how art and popular superstition preserved the true character of ancient deities as gargoyles, witches, and hobgoblins, eventually leading toward the decline of these phantoms under the gradual light of science and rational human evolution.
