Back in 1692 a fantastic army of witches struck Salem Village. "The houses of the good people," wrote Cotton Mather, were "filled with the doleful shrieks of their children and servants, tormented by invisible hands ... altogether preternatural."

Witches were a terrifying enemy. Invisible and powerful, they lurked anywhere, everywhere. Indians could be slaughtered without disrupting Puritan communities; but witches were neighbors, sisters, wives. The Salem Villagers panicked, tossed aside their own standards of justice, and plunged "into a blind man's buffet ... hotly and madly mauling one another in the dark." That is always the danger with invisible enemies - the hot, mad, buffeting society turns on itself.

None of this began with Salem Village or New England or the Puritans. Great witch hunts had convulsed Europe since the fifteenth century. In 250 years of witch hunting (beginning in 1479), the British killed some 30,000 witches. The stunning fact about these pogroms - in both the Old World and New England - is that both the hunters and the hunted were mostly women. Of course men ran the actual trials and justified them in learned treatises. The most famous disquisition blames witchcraft on "woman's insatiable lust" - and that was five centuries before Hollywood did the story.

Even before the Salem Village outburst, New Englanders had accused 123 witches and executed 16. In 1662, witch hysteria swept through Hartford after a young girl died and a pious woman broke into Dutch. But nothing in America ever approached the scope of the Salem Village trials - 144 accused, 19 hung, 4 dead in prison, 1 pressed to death with stones.

Witches gave Salem villagers an enemy to blame for the many troubles they faced - frontier war, smallpox epidemic, economic change, religious diversity. And witches were not much of a stretch in a seventeenth-century world filled with magic. Midwives knew strange potions. Cunning people foretold the future. People read almanacs, wore amulets and protected themselves from witchcraft by boiling pins in the urine of the bewitched (that flung the spell back on the witch). They flogged possessed animals and expected to see the scars on the witch.

But in the end, the Salem witches turned out to be untrustworthy enemies. Hunting them did not effectively rally the community against a shared adversary. The witches were too difficult to identify. They provoked too much uncertainty. Husbands denounced wives, brothers turned on sisters, friends on friends. Dogs were killed, a five-year-old girl jailed for eight months. Even the governor's wife, Lady Phips, got named a witch.

In 1692, the moral diagnosis of social trouble boomeranged right back onto the ministers. The witch hunt got out of control. Respectable citizens used the witchcraft embarrassment to fling Enlightenment notions into the minister's faces. Thomas Brattle, an influential Boston merchant, put it directly: "Salem superstition and sorcery" was "not fit to be named in a land of such light as New England is." The "ages will not wear off that reproach and those stains" which the "ignorance," "folly," and "barbarous methods" of Salem Village justice "leave ... on our land."

Still, the witch metaphor - scary, hidden, subversives - would remain an enduring American reflex. The Joseph McCarthy red scares are the most famous latter-day instance. Three decades earlier (in 1919-20), Attorney General A. Mitchell Palmer rounded up thousands of foreign-born radicals during the first great American red scare. A decade before that, in the waning of the Victorian era, Americans panicked over the terrible danger "white slavers" posed to innocent women.

The original witch hunt exposed the gap between old Puritan ideas and a changing society. But the urge to blame scary socioeconomic changes on moral villains would live on. The search for moral villains remains as fresh as today's newspaper, as powerful as any social movement on the contemporary scene.