satan
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In a recent interview in New York magazine, Supreme Court Justice Antonin Scalia acknowledged his belief in Satan.

Scalia said that "I even believe in the Devil.....Of course! Yeah, he's a real person. Hey, c'mon, that's standard Catholic doctrine! Every Catholic believes that.... In the Gospels, the Devil is doing all sorts of things. He's making pigs run off cliffs, he's possessing people and whatnot. And that doesn't happen very much anymore.... What he's doing now is getting people not to believe in him or in God. He's much more successful that way."

Dualistic theology - the idea that the world is divided into two parts, good and evil, and that humans are affected by a constant struggle between the two for domination - is common to many religions, and especially prominent in Roman Catholicism.

Though the Catholic Church has gradually moved away from more traditional and literal interpretations of Hell and Satan, Scalia is not alone; according to a 2007 Baylor Religion Survey, over half of Americans (54 percent) "absolutely believe in Satan."

In their book "Paranormal America," sociologists Christopher Bader, F. Carson Mencken, and Joseph Baker note:

"Americans are deeply divided on the nature of evil. Researchers have found that a person's views about the nature of evil and the role of evil impact other behaviors and beliefs. For instance, beliefs about Satan were a strong predictor of participation in social movements, rallies, petitions, pickets, and membership associated with the Moral Majority. More recently, strong views of religious evil have been found to be associated with intolerance of homosexuality."

During the 2008 run-up to the presidential elections, then-Senator Barack Obama was asked by pastor Rick Warren if he believed in evil.Obama replied, "Evil does exist. I mean, I think we see evil all the time. We see evil in Darfur. We see evil, sadly, on the streets of our cities. We see evil in parents who viciously abuse their children."

While much in religion and theology is considered metaphorical and allegorical, as Scalia noted belief in Satan as a literal incarnation of evil is common among many Roman Catholics. Fundamentalist Christian literature contains countless books describing Satan, demons, and devils as real, literal, incarnate entities that cause a wide variety of ills ranging from marital strife and "unclean thoughts" to depression, disease and death.

Belief in a literal Satan also plays an important role in Christian eschatology, the study of end-of-days prophecies. Those who believe that the end times are upon us have been especially popular.

Perpetual doomsayer Hal Lindsey wrote a best-selling and influential 1972 book titled "Satan Is Alive And Well on Planet Earth" in which he discussed - and cited evidence of - a literal Satan walking among us. A quarter-century later Tim LaHaye and Jerry Jenkins hit on similar themes in their "Left Behind" books that sold over 65 million copies and remain one of the best-selling fiction series in print.

Many Christians also believe that occult divination tools such as Tarot cards, pendulums, and Ouija boards can connect with, and even summon, evil spirits including Satan. Some even promote conspiracy theories involving Satan, claiming for example that credit cards and bar codes are not only "marks of the Beast" (i.e., Satan), but signs of an impending and demonic New World Order.

This is part of a broader trend of biblical literalism. Many believe that Earth was created by God in only seven days, in the case of so-called "intelligent design" creationism, less than 10,000 years ago. Another common belief is that Noah's Ark really existed (and that it's periodically re-discovered on a Turkish mountain), and so on.

In Roman Catholicism bread and wine are believed to literally - not just figuratively - become the flesh and blood of Jesus as soon as the faithful put it in their mouths, in a process called transubstantiation. (Of course it is possible to scientifically determine that this does not in fact happen - an x-ray or a stomach pump could easily show that the sacrament of the Eucharist does not literally change from bread to human flesh when consumed.)

People still believe in the Devil because there's still a need for him to exist. He still plays an important role in many people's belief systems and even daily lives. Writer and Christian apologist C.S. Lewis, in his 1942 book "The Screwtape Letters," wrote:

"There are two equal and opposite errors into which our race can fall about the devils. One is to disbelieve in their existence. The other is to believe, and to feel an excessive and unhealthy interest in them. They themselves are equally pleased by both errors."