In this passage, we read about the Holy Spirit and evil spirits. The Bible makes very matter-of-fact statements about both. Evil spirits exist but are subject to the direct and delegated authority of God. In fact, as the sons of Sceva discovered, evil spirits know Jesus and about his followers, they know who has authority over them. A child of God has to be filled with the Holy Spirit and, as a result, will be able to discern and deal with evil spirits.