He's heard the voices speak in ancient Greek. He's heard them speak in Latin. Dr Richard Gallagher says they converse in Chinese, Spanish, French; that they're wildly smart and manipulative.
The voices and the languages come out of people, he says, but they're not actually human.
They're demons. They're real, and so is evil, he says. Demonic possession exists, and he has seen it firsthand.
"They're fallen angels," Dr Gallagher tells DailyMail.com.
"This is what I literally believe. They're extremely bright; they're much brighter than humans. They've been around for millennia – so they speak all languages.
"I've heard them speak Chinese; I've heard them speak ancient Greek, which I studied," says the former Princeton Classics major. "I've certainly heard them speak and understand Latin."
The spirits do it, the psychiatrist says, "probably to freak you out or to show off – to boast."
The most striking thing about Dr Gallagher, before he starts to describe demons, is his imposing 6'5 frame as the psychiatry professor stands in the doorway of his office in suburban New York. He is reservedly polite in the small space, where greeting cards sit on a table and family photos adorn a window ledge, and he beckons to a low couch adjacent to a desk laden with files and papers. The window is bookended by shelves of psychiatry and medical journals and books.
In his 60s, Dr Gallagher's long limbs are clad in a blue blazer and khakis. He is extremely guarded about his own details, saying only that he has "a family" and siblings – he estimates he's treated 25,000 patients over the years. Not one who walked through his door was actually possessed.
Instead, the cases he's seen of possession and "oppression" – which is different and involves demons harassing an individual rather than taking control of them, he says – have all been referred to him, usually by exorcists. He's not even sure how it started a quarter century ago.
"I didn't volunteer, particularly, to get involved in this stuff, evaluating people for possession, demonic attacks," says the New York native, who has written a forthcoming book about the subject and his experiences called Demonic Foes: Experiences of a Psychiatrist in the World of Exorcism.
"I was just asked to do it, and maybe people thought I was open-minded or whatever. Probably people knew that I was a practicing Catholic, but I never volunteered for it – and, you know, slowly, I just began [to be thought of as] sort of an expert."
The first case he saw involved a victim of "oppression," a Hispanic housewife and mother from the American West who was being assailed by demons. She was an incredibly devout and charitable Catholic, Dr Gallagher tells DailyMail.com, but that exact holiness can sometimes open the door for an attack by evil.
"She and her husband both swore that she would be lying in bed, and all of a sudden, she would have the feeling of being assaulted by evil spirits, and bruises would appear on her body – so I needed to do a medical workup," Dr Gallagher says. "I needed to make sure she didn't have some clotting difficulty or something like that. I needed to asses her psychiatrically.
"She appeared to a very wonderful, devout, charitable person," he says, calling this woman and her husband "salt of the earth people."
"I just came to believe their story, and I can't say I knew a lot at the time about cases which a lot of people, including myself, tend to call a case of 'oppression.'"
He explains: "In possession, an evil spirit controls that person, takes them over – whereas with oppression (people use different terms for it, some people use the term "vexation") … that indicates an attack by an evil spirit on an individual, but the evil spirit can't or doesn't take over their personality.
"It's not random at all; there's almost always a discernible cause. The most common cause … is someone has turned to evil or the occult. And paradoxically, it's often when they try to get away from that the demonic world feels they have a hold on that person. That person may have actually even promised themselves to Satan or some kind of evil, and then they, in a sense, they're getting punished for trying to move out of that. That's the most common reason people get attacked."
He adds: "A lot of it depends on their internal intention. Are they kind of really, really committed to the occult, as opposed to just kind of playing around with a Ouija board?
"There are a couple of other categories of people who can get attacked – very holy people. And there are many stories of saintly people throughout history that had demonic' problems," he says.
When it came to the middle-aged housewife from the West, he says he believes she was oppressed by evil 'precisely because she was so holy and was doing incredibly charitable work with people.
"I think she was attacked because the demon didn't like her level of sanctity."
He says: "All her medical tests were negative; her bloodwork was all normal. She didn't appear to have any other medical or psychiatric illness … She just did not appear to be a psychiatrically troubled person at all.
"She had children, she had a normal family – and so I remember, when the priest said to me: 'Dr Gallagher, that's what I thought, but we wanted to make sure that we checked her out medically,' I said, 'Well, Father, you know I'm pretty sceptical.' And he said, 'That's the type of person we wanted.'
"So then he continued to send me things; he and his colleague, who was an ex-Marine, who had also become a prominent exorcist … I actually became very good friends with them. They're both deceased now, but I miss them terribly."
Before that first case – and his relationship with exorcists and the demonic world – he says he was unaware of the intricacies of possession and oppression.
He grew up a devout Catholic, one of five children born to an Irish-American lawyer and his homemaker wife. Dr Gallagher attended weekly Mass with his family and studied at renowned Catholic high school Regis in New York City before being accepted to Princeton.
"I didn't know what I wanted to be,v he says. "I probably wanted to become a lawyer, a professor or something. I did like helping people, you know – so when I was at Princeton I had a number of roommates who were pre-med, and I just got interested, intrigued by the idea of becoming a doctor. And I've also read a lot in my life, so I got interested in psychoanalytic ideas, and it just kind of dawned on me that helping people, as well as becoming a professor, would be interesting if I did it as a professor of psychiatry. So that's what I decided to do."
He laughs: "I'm the black sheep who became a psychiatrist in an Irish Catholic family."
Following Princeton, he played semi-professional basketball in France and taught English at a French high school. Then he trained as a resident in psychiatry at the Yale University School of Medicine, and he is currently on the faculty at New York Medical College and Columbia University Psychoanalytic Institute for Training and Research.
It was as his career progressed, however, that his acquaintance with the world of evil spirits intensified. He says he's seen about four cases a year, though he's heard of hundreds more, especially at meetings of the Europe-based International Association of Exorcists.
He mentions the case of another US housewife, though he does not specify her location. This woman – he gives her the pseudonym of Catherine - "as a teenager had dabbled in satanic rituals, and she had kind of promised herself, in some fairly foolish way, to evil spirits," he says. "She did a few grisly things, which I'm not going to go into, but she also, with a couple of friends, they did minor satanic rituals and she became possessed.
"She was certainly violent when the evil spirit took over, and she had a variety of signs of possession. It took multiple, multiple people to hold her down during exorcism."
He adds: "She had a very odd symptom, which is similar to a case in the gospels, where she selectively couldn't hear certain things … If you said to her: 'Catherine, did you go to the store today?' Shey'd say 'yes'. 'What'd you buy?' 'Meat and potatoes.' If you said, 'Catherine, did you go to church today?' She would say, '"What?' 'Catherine, did you go to church or did you pray today?' 'Did I what?'
"Her sense of hearing was blocked. So we had the bright idea – I was with a fellow psychiatrist, we were assessing her – and we had the bright idea, why don't we write it on a piece of paper?
"So we wrote it on a piece of paper: What did you do this morning? And she said, 'Well, I drove the car to the gas station, I had to fill up the gas tank.' 'Catherine, did you pray today? Did you go to church?' and hold it up on a piece of paper.
"Do you know what she said to me? She said, 'Dr Gallagher, why are you doing this?' I said, 'What do you mean?' 'Why are you showing me a blank piece of paper?'
"Now the obvious motive there was to prevent her from being able to talk about anything spiritual, get the help that she needed, get the solace and spiritual support she needed."
The evil spirits take hold of people, he says, because they truly hate God and humans.
"We have the ability to love and turn to God; they don't. They made their choices, and they hate the image of God in human beings," he says. "They truly seem to hate human beings. I mean, not only do they want to destroy us spiritually, alienate us from God, but they seem to take almost a sadistic pleasure in destroying us as creatures who can still turn to God, to their enemy, creatures who can also still love, which they don't seem capable of anymore. They've rejected the whole idea of goodness and love in a kind of perverted way."
He says the demons exhibit extraordinary powers such as personal knowledge and near clairvoyance. On one occasion, a demon told him how his mother had died – ovarian cancer. That evil spirit also knew "how 15 other people's parents died, too. It wasn't just me."
On another occasion, a demon told him exactly what a priest was wearing though the clergyman was nowhere near Dr Gallagher and the possessed person speaking. In a different case, Gallagher was also personally addressed.
"I had a demon say to me: 'How's that book going? It won't do any good' … that's when I was first thinking of writing a book. So I've had demons come and they've said they hate me, but again, I think they hate all Christians … they certainly put more of their energy in saying how they hate the exorcist. That's their real target, not me."
He tells another story of a woman in her 30s, a member of a Satanist cult who was thinking about leaving – which is when the evil spirits took over her body.
This woman "was in the back of a car once, and I was with the exorcist, and she went into a trance," he says. 'She was unequivocally possessed … and I heard her in the back seat of the car.
"She came out with some vile stuff – 'Leave her alone you f*****g priest', that sort of thing, and this went on for about five minutes. Then she came out; she had no remembrance of it at all."
He continues: "I never went to her exorcisms, because I was busy … but the priest would invite me to come to the exorcism. It wasn't around here. And I'm on the telephone line, this is a landline, with the priest at the time, and he says, "You know, Rich, can you make this exorcism session?" And then, during that phone conversation – and this woman was hundreds of miles away … that same voice came in on the phone and it said "Leave her alone, leave her alone, you f*****g priest. She's ours, she's not yours." And I did hear that. That was creepy."
He says that, despite his work and beliefs regarding demons and possession, he has 'never felt particularly harassed or discriminated against, because Americans tend to be kind of a tolerant, pluralistic people.
"In the larger society, it's not a fringe belief," he says. "This is actually a mainstream belief. Opinion polls show that probably about 60 percent and upwards – probably about 70 percent of America – believe in the devil, and the majority of Americans … believe in evil spirits and demons have some ability to directly attack human beings.
"People will sometimes say to me, 'How do you feel about talking about a fringe belief?' I say, 'It's not a fringe belief.' I'm more mainstream than skeptics. The other thing about skeptics is, the extreme skeptics, they've never seen a case.
"They come up with all kinds of cockamamie theories … they say, 'Well, you know, this person heard Latin babbled as a kid.' But it's kind of absurd. The demon is speaking fluent Latin and is understanding fluent Latin, and many of these people are not even Catholic, didn't even go to church as a kid."
He adds: "I understand believing in evil spirits is not a very comforting belief, and it has implications that, you know, we don't want to accept. Having said that – and there's plenty of alternate theories; I don't think that those theories usually hold water – and when you've seen some of these cases, you realize that this is clearly not something that could be explained by psychopathology or trickery or anything like that."
And, despite having witnessed evil and his interactions with demons, he says he's not particularly worried that they'll come after the psychiatrist himself; he's bolstered by his faith and the faith of others.
"I have a lot of people praying for me," he says.
"I'm not seeing the devil everywhere," he explains, adding: "I always tell people it's an equal mistake to see the devil everywhere as to deny the devil exists."