Discernment of Spirits
Basically, this is a gift of the Spirit, which allows the recipient minister to judge whether a motivating spirit of someone is of good or evil origin. (Acts 13:9-10) Good spirits emanate from God's domain because He does not author any unwholesome thing. Evil spirits originate from Satan's rebellion and owe their instruction and allegiance to him. When man allows himself to be seriously influenced by Satan, usually by misuse of his agency through spiritual carelessness or rebellion, he may temporarily become capable of doing terrible acts. We often say of such news stories, "How could anyone do such a horrible thing?" It is possible that Jesus chose to inform us of the destructive capability of evil spirits when he caused his disciples to write of casting out the evil spirits (devils) from a long deranged man. These spirits then went into a nearby heard of swine which suddenly went from peaceful grazing to complete terror, and together ran down the hill into the Sea of Galilee and drowned. (Matt. 8:29-33, Mark 5:1-13, Luke 8:26-35) The normal instinct for preservation of life in these swine was somehow overcome by the displaced spirits.