A book by Elaine Pagels (Random House, 1995; Vintage, 1996). In this book Pagels, known best for her popular book The Gnostic Gospels, explores how Satan evolved from the peculiar figure of The Adversary in the old testament, an entity who was opposed to God rather than an angel working His will, and into a figure with almost the power and nature of God himself, the embodiment of all the evil in the world.

In this book Pagels puts forth the idea that Satan was used as a knife of sorts, a dividing line between what was right and what was wrong. Because the Satan was the closest thing to God that was not God, he became emblematic of that which is closest to being righteous, those that are closest to following the right path, and yet who do not. By pointing out the differences in these others, early christians showed exactly what was wrong, and thus the most minor of differences became the most major of transgressions.

The book illuminates, to a degree, how Christianity, originally a sect of judaism distanced itself from the rest of Judaism and how orthodoxy formed out of the mass of early christian sects, the orthodoxy that was ultimately recorded by the Nicene Creed. The book shows how, ultimately, the antisemitism present even in some of the Gospels, the literal demonization of the Jews by early christians, was an inherent part of the formation of christian identity and manages to do it from an unbiased, academic viewpoint that does no demonizing in and of itself.