(Luke 17:20-21 ESV)
Jesus' prophecy about when the kingdom of God will come is the kind of statement no one likes to hear and yet all of us secretly fear. At the root of it, Jesus is saying the same thing to the Pharisees that Isaiah said to the people of his day: ‘Keep on hearing, but do not understand; keep on seeing, but do not perceive.’
We have a great deal of trouble understanding what the Kingdom of God is ourselves. Part of the reason is that most of us have never lived in the sort of kingdom Jesus is talking about. In his day the Caesars allowed themselves to be worshipped as gods because their self-understanding and what they communicated to the people was that Caesar was the kingdom. There was no empire without the emperor. The people essentially existed to advance the interests, power, and fame of the king.
The Roman Republic lasted from around 509 BC to 27 BC when Octavian proclaimed himself Caesar Augustus, literally "majestic king." Caesar was not his name. He had been adopted by Julius Caesar, essentially anointing him as successor to the throne. Augustus wasn't his name either, but was an honorific title, and he ruled from 27 BC to 14 AD. Here was a man who had accumulated so much power in himself that he literally was the state for all practical purposes. The problem with such an arrangement is that there is a great tendency toward megalomania in people like this. The last major world ruler to adopt such a style was, of course, Adolf Hitler.
So we have to ask a serious question here. Was Jesus aware as he was speaking to the Pharisees that he was inferring that in just the same way the Caesars were understood to be the "kingdom of Rome", if you were looking for the "kingdom of God" you didn't need to look any further than himself. The people who are part of the kingdom of God are to be understood as an extension of Jesus being and person, and every place where the people of the kingdom are is kingdom territory -- also an extension of the person and work of Jesus. Did Jesus really mean to communicate this?
The answer is a troubling "Yes". Troubling, because the only examples we can seem to find in history of people claiming such a position are fanatical dictators who end up bringing the whole dynasty down upon themselves as they become more and more self-absorbed. This leads directly to the problem voiced by C.S. Lewis in Mere Christianity,
I am trying here to prevent anyone saying the really foolish thing that people often say about Him: "I'm ready to accept Jesus as a great moral teacher, but I don't accept His claim to be God." That is the one thing we must not say. A man who said the sort of things Jesus said would not be a great moral teacher. He would either be a lunatic--on a level with the man who says he is a poached egg--or else he would be the Devil of Hell. You must make your choice. Either this man was, and is, the Son of God: or else a madman or something worse. You can shut Him up for a fool, you can spit at Him and kill Him as a demon; or you can fall at His feet and call Him Lord and God. But let us not come with any patronizing nonsense about His being a great human teacher. He has not left that open to us. He did not intend to.
If you read beyond Luke 17:21, you'll see just how clearly Jesus understands what he is implying: “The days are coming when you will desire to see one of the days of the Son of Man, and you will not see it. And they will say to you, ‘Look, there!’ or ‘Look, here!’ Do not go out or follow them. For as the lightning flashes and lights up the sky from one side to the other, so will the Son of Man be in his day."
Here then is the question you have to answer personally. Was Jesus insane when he claimed to be the embodiment of the Kingdom of God? Was he crazy to assert that all of his subjects (we call them "followers" today) are, in reality, the embodiment of his person in the world? Was he simply another fanatic whose "kingdom" ultimately came crashing down on him because of his own self-importance? Or was he really the true Majestic King? And if so, have you yet literally fallen at his feet and called him Lord and God?