(the following written by Charles Ryrie)
Definition of Demon Possession:
Demon possession means a demon residing in a person, exerting direct control and influence over that person, with certain derangement of mind and/or body. Demon possession is to be distinguished from demon influence or demon activity in relation to a person. The work of the demon in the latter is from the outside; in demon possession it is from within. By this definition a Christian cannot be possessed by a demon since he is indwelt by the Holy Spirit. However, a believer can be the target of demonic activity to such an extent that he may give the appearance of demon possession.
Effects of Demon Possession:
1. Sometimes physical disease (Matt. 9:32-33), but physical disease and demon possession are dinstinguished in Scripture (Acts 5:16).
2. Sometimes mental derangement is due to demon possession (Matt. 17:15) but not always (Dan. 4).
Extent of Demon Possession:
1. As to persons. Only unbelievers may be possessed. In the time of Christ, most instances of demon possession were among non-Israelites.
2. As to time. Usually there is an outbreak of demon activity when truth and light are the strongest (e.g., time of Christ).
[According to scripture:]
Demons attempt to thwart the purpose of God.
Demons extend the authority of Satan by doing his bidding.
Demons may be used by God in the carrying out of His purposes.
Demons can inflict diseases.
Demons can possess men.
Demons can possess animals.
Demons oppose the spiritual growth of God's children.
Demons disseminate false doctrine.
