I have been running up against the difference lately between authority and power.
Satan undeniably has power. He has power to destroy in so many devastating ways. He has power to prevent growth. Picture the most devastating kinds of relational damage -- the heroin addict that compromises and betrays every love, every relationship, for the sake of an addiction; the marriage that can never quite get past defensiveness and self pity and fear, and prevents so much joy and fruitfulness because of those self-protective patterns; the parent who over-indulges their child and prevents them from growing strong and vibrant and blessed; the fearful lover (or parent or boss or teacher or ...) whose insecurity demands rigid control of the one who should be loved and set free.
All of these examples -- and of course there are thousands more -- demonstrate power exercised without, or in contravention of, legitimate authority. (FWIW, control is always at odds with love.) And whether demonic forces are directly involved or not, each of these thousands of examples are exactly what Jesus described in John 10 -- that the thief comes to steal, kill, and destroy the abundant life God longs to give his creation.
I spent a few hours yesterday afternoon cutting buckthorn. There's a beautiful trail back in the woods east of my place that has been choked by the invasive, tangly stuff. At one time it was a wild, remote haven for people to pull in their RVs and camp in the isolation of a beautiful woods. Buckthorn has closed off the trails, cramped the campsites, and choked out native species. So I got my pole trimmer out and spent a couple hours clearing one specific trail. It felt a little like spitting in the wind, but it's probably better than just letting the awful stuff grow without protest. Buckthorn has no authority to be here. It's an invasive species and everybody agrees it's bad, but it has tremendous power. Left unchecked it will dominate a plot of land and completely take over.
Jesus doesn't give his followers a lot of power. But he does give them authority. And when, after exercising that authority (v. 17) the disciples are pumped up on what they perceive as their power, Jesus reminds them that it is authority he has given.
Satan has no authority unless we invite him in. Unless we agree with his lies, he has no right to exercise his power over us. He will certainly try, but we can stand in our rightful identity as children of God, bought by the blood of Jesus, and in spite of our weakness, claim the authority of Jesus himself. It's an important distinction. We most often measure ourselves based on our perception of power, but God's word makes clear that he values our weakness (see 2 Corinthians 12). In some way, Jesus delights to exercise his power as we stand, utterly defenseless, in his authority that he has given us.
One of the most vivid examples of this is the apocalyptic battle in Revelation 19, sometimes described as the "battle of Armageddon" -- really just a name of a plain in the north of Israel that was a famous battleground in ancient times. (Note, at the risk of derailing this whole train of thought, I don't believe this is about a future prediction, so please don't get caught up in ideas about Russian tanks rolling into the north of Israel and all that. If you want to talk about how I interpret Revelation, I'm happy to do that. Just let me know.) In the account in Revelation 19, all the armies of light and darkness line up, prepared to do battle, clashing swords against shields, shouting battle cries, scavenger birds circling overhead ... and the battle is decided when Jesus rides out on his horse and speaks a word (that's the sword that comes out of his mouth, in Revelation's obscure imagery) and defeats all the battalions of hell. In other words, we're there, we're at the battle site, but we're just spectators. Cheerleaders. We don't exercise power, Jesus does.
This is a game changer. What does it mean to stand in your identity and authority as a child of God today? What does it mean to really believe a) that God calls you his beloved son or daughter in whom he is well pleased, and b) that he gives you authority to stand against all the forces of hell, implicit and explicit? This is worth pondering. This gets right to the heart of what it means for us to proclaim what Jesus called "the kingdom of God."