Question: "How are Catholics able to perform exorcisms if many of their beliefs are unbiblical?"
Answer: In movies such as The Exorcist and The Exorcism of Emily Rose—both of which are loosely based on actual events—the demons are cast out by Catholic priests. This has caused some to wonder, if such exorcisms are true, how they could be performed by Catholics, since Catholics are not Christians.
First of all, the statement “Catholics are not Christians” is too broad. The Catholic religion teaches much that is contrary to God’s Word, but sincere believers still exist within the Catholic Church and do much good in the world. Being a Catholic does not make one a Christian, but neither does it prevent one from being a Christian. Please read the following articles: "Is Catholicism a false religion? Are Catholics saved?" and "I am a Catholic. Why should I consider becoming a Christian?".
Second, miracles can be counterfeited (2 Thessalonians 2:9). Jesus said that some who are not truly His may still perform miraculous signs—including exorcisms—in His name. In Matthew 7:22–23, Jesus warned, “Many will say to me on that day, ‘Lord, Lord, did we not prophesy in your name and in your name drive out demons and in your name perform many miracles?’ Then I will tell them plainly, ‘I never knew you. Away from me, you evildoers!’” On Judgment Day, there will be those who had cast out demons and thought they were saved because of all their good works. They had adopted the mannerisms of Christianity and given mental assent to its doctrines, but they were Christians in name only. They had never surrendered their lives to Christ. At the judgment, these nominal Christians will find their outward show of spirituality will not be enough to earn them entrance into heaven; whatever miracles they performed were empowered by something other than the Holy Spirit. Unfortunately, many people today hold the dangerous philosophy that good works can earn salvation.
Satan has a certain amount of power that he uses to deceive and distract. The magicians in Pharaoh’s court were able to replicate many of the miracles Moses performed (Exodus7:22; 8:7). However, there was a limit to what their magic could accomplish, and God’s power overwhelmed their tricks (Exodus 7:11–12). It could well be that Catholic exorcisms are similar “miracles,” designed to lend credence to Catholic doctrine and “prove” the power of talismans and rituals.
Acts 19:13–16 gives an example of exorcists who did not know the Lord Jesus yet who tried to use His power to cast out demons: “Some Jews who went around driving out evil spirits tried to invoke the name of the Lord Jesus over those who were demon-possessed. They would say, ‘In the name of the Jesus whom Paul preaches, I command you to come out.’ Seven sons of Sceva, a Jewish chief priest, were doing this. One day the evil spirit answered them, ‘Jesus I know, and Paul I know about, but who are you?’ Then the man who had the evil spirit jumped on them and overpowered them all. He gave them such a beating that they ran out of the house naked and bleeding.” The true power is not in speaking Jesus’ name, sprinkling holy water, or touching a stole, but in knowing Jesus personally.
Demons are real. Satan is real. However, Satan is a master trickster and the father of lies (John 8:44; 2 Corinthians 11:14). A demon’s ability to lure gullible human beings into its traps often exceeds our ability to detect the traps (2 Corinthians 2:11; 1 Peter 5:8). If it would serve its purpose to hide within a human body, a demon might do that. Or, if it would serve its purpose to pretend to come out on command, it might do that, too. Satan could very well participate with an unsaved exorcist in order to inflate the exorcist’s pride and boost confidence in his power over evil. The purpose for “staging” an exorcism might be to more deeply entrap those who come to Catholic leaders for help.
The only power that is guaranteed to defeat Satan every time is the power of the Holy Spirit residing within a believer who is equipped with the armor of God (Ephesians 6:11–17; 2 Corinthians 10:4). As we submit to God, we can “resist the devil, and he will flee” (James 4:7).