The recent movie The Pope’s Exorcist has done much to renew public interest in angels, demons, and exorcism. The movie is based on two books by Father Gabriele Amorth, An Exorcist Tells His Story, published in 1990, and An Exorcist: More Stories, published in 1992. The two books provide a biography of Amorth, the Roman Catholic Church’s most famous exorcist who is known as the James Bond of exorcists. In his career as the chief exorcist of the Diocese of Rome, Amorth claimed to have conducted over 60,000 exorcisms.

People who know that I’ve traveled and spoken globally for decades have asked me what I think about demon possession and exorcism. I offer these thoughts as a scientist and a Christian with some experience in this spiritual realm.

Angels and Demons
Angels are supernatural, intelligent beings. They are a fundamental component of every theistic religion. In Christianity there are two categories of angels: (1) those who are righteous and serve God, and (2) those who are evil and in rebellion against God. The latter are referred to as fallen angels or demons.

According to Job 38:4–7, angels were present when God laid the foundations of Earth. The Bible is silent on how much time transpired between the angels’ creation and their witnessing the laying down of Earth’s foundations. It is possible that God created angels before he created the universe.

The Bible declares that Satan is the most powerful of the angels. He was the first being and the first angel to rebel against God. Exactly when Satan’s rebellion occurred we do not know. The Bible does seem to indicate (Revelation 12:3–4, ESV) that Satan persuaded a third of the angels to join him in rebelling against God. Thus, according to this passage, two thirds of the angels are righteous and allied with God and the remaining third are wicked and enemies of God.  

According to the Bible, angels, both righteous and fallen, inhabit and operate in a dimensional realm that is distinct from the cosmic space-time dimensions. However, while humans are constrained to the space-time dimensions of the universe, angels are not. The Bible indicates that angels, both righteous and fallen, can enter and exit the human realm at will. They can enter immaterially or materially. They can even appear in human form. Biblical examples of angels appearing materially can be found in Genesis 18–19, where both Abraham and Lot (on separate occasions) served food to angels that the angels ate. 

Do Angels and Demons Really Exist?
I have been to places in the world where nearly everybody believed in angels and demons and a large fraction of the people claimed to have personally encountered angels and/or demons. I also have been to places in the world where very few people believed that angels and demons exist and no one claimed to have an angelic encounter. Examples of the former would be rural parts of Africa during the 1980s and the Soviet Union of the late 1980s. Examples of the latter would be many parts of present-day America and western Europe.

Given what the Bible says about demons, this dichotomy of belief about angels is not at all surprising. Satan and his army of demons employ two strategies in their attempts to prevent humans from receiving God’s offer of redemption and eternal life. Their first strategy is to persuade humans that there is no supernatural realm. A key component of this strategy is for them to remain hidden. Their second strategy is to overwhelm and terrify humans with their supernatural powers so that humans will be motivated to appease them.

Discerning the Physical from the Psychological and from the Demonic
One of the things I most appreciated about Amorth’s writings is his statement that 98% of the people who came to him with the concern that they were possessed by a demon needed a psychiatrist or a therapist, not an exorcist. Mental illnesses appear to have risen dramatically since Amorth made that statement. Therefore, the percentage today is likely even higher.

One of my sons is a clinical neuropsychologist. In his diagnostic work he first looks for physical brain abnormalities. Is there a brain injury, tumor, or brain chemical imbalance that is responsible for the patient’s mental distress or mental abnormality? He next looks for a genetic link. Was his patient born with one or more genetic mutations? If none of these factors explains the mental distress/abnormality, he then quizzes his patient about past traumatic events. After uncovering one or more major traumatic events, he then refers his patient either to a therapist or psychiatrist.

The same process my son employs needs to be applied to anyone who claims to be harassed, oppressed, or possessed by a demon. First, eliminate possible physical or chemical causes of the distress. Second, eliminate possible psychological causes. Then, and only then, pursue the possibility of demonic harassment, oppression, or possession.

Demonic Possession, Oppression, and Harrassment
The Bible does not explicitly state that Christians cannot be demon possessed. However, when one becomes a born-again Christian, the Holy Spirit takes up permanent residence within that Christian (Romans 8:9–11; 1 Corinthians 3:16, 6:19). The Holy Spirit will not share that residence with anyone other than the Christian. As 1 John 4:2–6 states, spiritual darkness is not inside Christians. 

For non-Christians to become demon possessed, they must grant permission to the demon(s). Permission is granted through involvement in the occult or through a close relative’s or a sexual partner’s involvement in the occult where that involvement has not been confessed to God as a sin that must be repudiated. Ephesians 4:26–31 explains that deep-seated, long-lasting bitterness, anger, or rage can give Satan and his demons a foothold into people’s lives.

Another way one or more demons can gain a foothold is when a person gives up control of his or her mind. That loss of control can occur through abuse of alcohol or drugs or through such mind-altering practices as hypnosis or mind-emptying meditation. 

Christians can be harassed or oppressed by demons when they pose a discernible threat to the demons. Such threats occur when Christians are ministering, or are seen as potentially ministering, to non-Christians who are being targeted, oppressed, or possessed by a demon or demons. In such circumstances the demons do what they can to scare the Christians away from interfering with their objectives. 

Personal Encounters
My first encounter with the demonic after I became a Christian occurred about two blocks from the campus of the California Institute of Technology (Caltech). I was walking back to the campus when a woman on the other side of the street started screaming obscenities. In the midst of those obscenities she shouted at me to stay away from her and not to come any nearer. I thought her shouts were strange since I never came within 50 feet of her and hadn’t looked at her or even in her general direction. When I did look at her, she fell to the ground into the fetal position, began to shake with fear, and repeatedly yelled for me to go away. 

When I got back to Caltech, I talked to fellow astronomer and devout Christian, David Rogstad, who currently works part-time for Reasons to Believe. He explained to me that I had encountered a woman who was demon possessed and that the demons were worried that I intended to cast them out.

A couple years later, I and a recently converted Christian were visting people who had filled out registration cards at our church indicating that they had attended for the first time. One of those visits was to a woman who was living in a witchcraft coven. The leader of the coven, a warlock (male witch), was holding six women captive in his house as sex slaves. We noted that the six women were terrified of him and even more terrified to attempt to leave him. More specifically, they were terrified of the demons living within him. 

When the coven leader learned that we were Christians, he bragged that he knew the Bible better than we did. He asserted that he had the entire New Testament memorized and could quote any verse forward or backward. He challenged me to pick a verse from the Bible for him to quote. I responded by challenging him to pick any verse from the New Testament and to explain to us what that verse means. We quickly found out that he was unable to discern the meaning of any Bible verse. Though the demons within him performed miracles in front of us, it was obvious that they were devoid of truth. 

Several of us Christians committed to praying and fasting and, in time, all six women were able to escape the clutches of the coven leader. A few months later, a police raid resulted in the coven being shut down, though I suspect it may have simply moved to a different city.

That same year, I had another encounter. A young man began to intermittently attend one of the Bible studies I taught. His actions, words, and lack of self-control made it obvious to the Christians in the study that he was demon possessed. At one of our Bible study sessions he claimed he wanted to be delivered. After the study, several of us gathered around him and prayed intently in the name of Jesus Christ for the demon to be cast out. Suddenly, the young man began to speak and behave like a normal human being. His facial expression and body language immediately changed. No more charges against Jesus Christ of despicable immoral acts came out of his mouth. He had self control. However, when we asked him if he was willing to receive Jesus Christ as his personal Lord and Savior, he said, “Not yet.” Within days, we discovered that his parents, who were both heavily involved in the occult and much opposed to Christianity, were very angry at what we had done—reminiscent of the account in Acts 16:16–21 of the owners of the slave girl who had been delivered from a demon. 

For the following two weeks, the young man’s words and demeanor were morally exemplary. However, during the following third week, his actions, behavior, and words were even more abhorrent and evil than they were before our prayer gathering for him—reminiscent this time of Jesus’s warning expressed in Luke 11:24–26. 

We told the young man that we would continue to pray for him, but until he was truly willing to be delivered from the demons he had invited into his being and until he was willing to repent of his sins and receive Jesus Christ as his personal Lord and Savior he was not welcome to attend our Bible study. We never heard from him again.

In chapter 9 of our book, Always Be Ready, I write about my encounter with demon possessed philosophers during two lectures I gave in Kiev, Ukraine, when Ukraine was still under the tight control of communists, the KGB, and the Soviet Union. During my 11 years as minister of evangelism at Sierra Madre Congregational Church (now Christ Church Sierra Madre) and my 36 years as president of Reasons to Believe, I had several other encounters with people who were either demon possessed or demon oppressed.

Responding to the Demonic
My consistent counsel to Christians is that when they encounter the demonic, the first thing is to deal with it prayerfully and carefully, but never seek it out. There are too many people who are eager to hear and respond to the Christian gospel message for us to spend an inordinate amount of time on people who are resolute in their unwillingness to repent of their rebellion against God and to receive Jesus Christ as their personal Lord and Savior.

Second, I remind Christians that the demons are more powerful than we are. People can be delivered from demon possession and demon oppression only through the power of Jesus Christ. We are to cast the demons out through prayer in the name of Jesus Christ.

Some demons are more resolute and powerful than others. As Jesus warned, some can be cast out only through prayer and fasting (Mark 9:14–29). In such circumstances, gathering a group of Christians together in dedicated fasting and prayer is the key to seeing someone delivered from demons.

Third, exorcism should only be attempted when a person wants to be set free from demons, is willing to repent of the sins that invited the demons to come into their lives, and who is willing to receive Jesus Christ as their personal Lord and Savior. As noted above, I once failed to heed this advice to the detriment of the person I was attempting to set free. Jesus declared this counsel in his teaching Luke 11:24–26.

Finally, demons need permission to invade the life of a human. They are granted this permission when a human pursues the occult, places a higher priority on power than on truth, hangs on to deep-seated bitterness and anger, or gives up control over their mind through alcohol, drugs, and/or mind-altering practices. Delivering people from such pursuits is the first step to setting them free from the demonic. 

Occasionally, a demon or demons gain access to a human through the forbidden pursuits of a close relative or a sexual partner. In such cases, it is crucial for the person to confess the forbidden pursuits as sins and to agree with God that such pursuits are dangerous and against the will of God. Such confession will cut the demonic link between the person and his or her close relative or sexual partner. It is reassuring to know and understand that God only holds us responsible for confessing immoral pursuits that we’re personally aware of.

In the educated western world of the twenty-first century, any talk about demons may invite mockery. Such disdain for the spiritual realm is consistent with the state of human beings who are in rebellion against their Creator. God is a spiritual being. May we be wise in our interactions with people and seek ways to show how they can be reconciled to God.

Check out more from Reasons to Believe @Reasons.org