What does Luke 11:23 mean?

But if I by God’s finger cast out demons, then God’s Kingdom has come to you.

“When the strong man, fully armed, guards his own dwelling, his goods are safe.

But when someone stronger attacks him and overcomes him, he takes from him his whole armor in which he trusted, and divides his plunder.

The unclean spirit, when he has gone out of the man, passes through dry places, seeking rest, and finding none, he says, ‘I will turn back to my house from which I came out.’

When he returns, he finds it swept and put in order.

Then he goes, and takes seven other spirits more evil than himself, and they enter in and dwell there. The last state of that man becomes worse than the first.”