Something bizarre occurred in the home of Ivy League–educated psychiatrist Richard Gallagher. Typically, his two cats got along well with each other. "But one night around 3:00 a.m., loud screeching sounds startled me and my wife out of our sleep," he said. "Our two normally docile cats were going at it like champion prizefighters, smacking and clawing at each other, intent on inflicting some serious harm." Even after they were separated, "they continued to growl and bristle." Gallagher and his wife were mystified. The next morning, as previously planned, a Catholic priest arrived on Gallagher's doorstep, accompanied by Julia, the self-described "high priestess" of a satanic cult. The plan was for Gallagher to examine her to determine if she really was possessed by a demonic spirit. Julia gazed at him with a smirk. "How'd you like those cats last night?" she asked. This was just one of the bone-chilling encounters that Gallagher has experienced in twenty-five-plus years of investigating demonic possessions and attacks. Calling himself "a man of science," he started out skeptical about the satanic realm. Then his firsthand work led him to conclude that there are some individuals who aren't mentally compromised but rather are under the influence—or even the temporary control—of malevolent spirits. What gives his conclusion particular weight is his professional standing as a physician trained in psychiatry at Yale University and psychoanalysis at Columbia University. He has been a professor of clinical psychiatry at New York Medical College and a faculty member of the Psychoanalytic Institute at Columbia University. No less an authority than Joseph T. English, past president of the American Psychiatric Association, called him "highly respected" and "superbly credentialed," with "unimpeachable integrity." As encouraging as it is to learn about angels and their guarding and guiding of people, it's daunting and disturbing to explore the world of "fallen angels," the pack of rebellious spirits that Christian theology says is led by Satan himself. These evil beings have turned the supernatural realm into a tumultuous battleground for the souls of people like you and me, an otherworldly dimension where malicious creatures scheme to snatch us before we can enter God's eternal embrace. "To the untrained eye, many possessions may be thought to fall into the psychiatric categories of various psychoses and severe personality and dissociative disorders," said Gallagher. "However, for well-trained psychiatrists and other health professionals, [demonic] possessions differ from such disorders in significant ways." Some skeptics have sought to discredit Gallagher's conclusion that demonic possessions are very real, although rare. However, naturalistic explanations seem facile and unconvincing in the face of eyewitness accounts. Clearly, a bias against the supernatural prevents some people from following the evidence wherever it leads, even if it points toward a supernatural reality. And of course, remarkably consistent beliefs about these malevolent spiritual beings can be found in cultures around the world and throughout history. "We live in a world that is both seen and unseen, and these two realms can influence each other in unimaginable ways," Gallagher said. "A segment of that invisible world seems to be mysteriously but remarkably hostile to human beings and seeks their physical and spiritual destruction. On rare occasions, like some kind of cosmic terrorist, that segment shows its true colors." The apostle Paul put it this way in Ephesians 6:12: "Our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms." In the United States, belief in the devil has dropped ten percentage points since 2001, although a majority—58 percent—still affirm his existence. In contrast, nearly one in three Americans is convinced that hell and Satan aren't real. "Scripture makes it clear ... that Jesus and his followers took demons seriously," said cultural anthropologist Charles Kraft of Fuller Theological Seminary. "They acknowledged their existence and used the power of the Holy Spirit to fight them.... In the gospel of Mark, for example, over half of Jesus' ministry is devoted to delivering the demonized."