Lots of folks seem to miss the point of sending out the Seventy; at least as it appears so to me. Some wonder which was more important: the sending out of the Twelve (Luke 9:1-10) or sending out the Seventy (Luke 10:1-16). Others liken the event to an evangelistic outreach, upon which our own ministries should be based. Still others get caught up in their having power over demons and exactly when Satan was cast out of heaven, and when Jesus actually did see his fall. Some of these things, of course, are mentioned in Luke 10, but the real point of it all seems to be far more significant than answering these questions.
The Seventy returned from their mission with great joy (Luke 10:17). They had been sent out as lambs among wolves (Luke 10:3), but since the Lord had given them authority over their enemies, no harm came to them (Luke 10:19). Therefore, they rejoiced in their victory over an otherwise unfriendly and, perhaps, influential portion of the people they ministered to. Although the disciple probably expected to meet with conflict, I don’t believe they anticipated such a complete and decisive victory over their opposition.
The conflict would have been a spiritual one, and the opposition would have come largely from the authority figures in the communities they entered, the same sort of authority figures who opposed Jesus (Luke 6:40; 10:16; cf. John 15:20). Yet, despite the inevitable persecution they must have endured from Jewish authorities, the Seventy rejoiced in their victory over demons. That is, they were victorious over whatever held the people captive, namely, over that which the Lord had given them authority (Luke 10:17, 19).
This calls into question what we define as demons. While we can usually agree that demonic possession is a form of spiritual wickedness, most people probably would not agree that spiritual leadership that opposes Christ is necessarily demonic. However, the **power** authorities have over people, who subject themselves to these authorities, when this power is opposed to Christ, must be seen as demonic power, in my opinion. For example, false doctrine is a strong delusion (cf. 2Peter 2:1; 2Thessalonians 2:11). If Jesus’ disciples had authority over the power of the enemy, they must have had power or authority to communicate the truth in a manner that destroyed or exorcised the people’s trust in false doctrine taught by their leaders.
A demoniac, viz. anyone opposed to Christ, may express his power over others through force (cf. Mark 5:2-4; Matthew 8:28), but others through leadership (cf. Luke 4:33-36). The one is controlled by an inner force and forces his will upon others, like a ruler of a country who rejects the Gospel. The second controls others through this same inner force, but, rather than forcing his will upon others, he indoctrinates his victims, getting them to trust his leadership / teaching ability. The Seventy were given authority over this type of activity.
Jesus told the Seventy that they should not rejoice in the fact that they had power or authority over demonic activity, but that their names were written in heaven (Luke 10:20). That is, Jesus was pointing to an ancient custom of keeping a record of the names of a city’s citizens. A public register was kept that families might be known for the purpose of preserving the line of inheritance etc. So, if Jesus’ disciples’ names were written in heaven, they enjoyed the advantages of being citizens of the Kingdom of God, and no earthly power had authority over anyone in God’s Kingdom. Rather, the citizens of God’s Kingdom spoke for him, and their authority prevailed over earthly authority whenever the two clashed. That is, whenever the interests of the Kingdom of God clashed with the interests of the earthly authority, God’s people have authority over that demonic power.