In The Exorcist, the possessed girl’s head rotates 360 degrees, she floats above the priests’ heads, and her bed shakes violently on its own. Any reality there? Where does evil come from? Is it solely within the human heart? Or is there some actual invisible malevolent force behind it? Satan, a laughingstock, or a nightmarishly real being? Recent polls show that 56% of us believe in Satan. To sort it out, we’ll look at the Bible, and religious scholarship, and popular culture, and some personal experience to see if there’s any credible evidence of a real being, an enemy of mankind out to destroy us.