14 And He was casting out a demon, and it was mute; when the demon had gone out, the mute man spoke; and the crowds were amazed. 15 But some of them said, “He casts out demons by Beelzebul, the ruler of the demons.” 16 Others, to test Him, were demanding of Him a sign from heaven.
If you recall from Matthew, this is the incident that Matthew links with the idea of an unpardonable sin. It is not a sin of simple unbelief, but a sin of willful disbelief. The Pharisees, the religious men of the day who read their bible regularly and claimed to know God, were looking about the works of Christ, who was healing the sick and helping those in need, and they could not accept that this was the work of God, because Christ disagreed with their conduct, their lifestyles, and their traditions that they held dear.
So despite being presented with the miraculous that does great good, the mind of the Pharisee attributes it to evil. Or when presented with such signs, the other Pharisees who want to appear to be more reasonable and open-minded continue to demand more proof from Jesus. Not that any amount of proof would be enough, because both sects had already made their decision. They were willfully continuing on in unbelief because it would be too inconvenient for them to admit their error.
Jesus addresses the most hostile group first:
17 But He knew their thoughts and said to them, “Any kingdom divided against itself is laid waste; and a house divided against itself falls. 18 If Satan also is divided against himself, how will his kingdom stand? For you say that I cast out demons by Beelzebul. 19 And if I by Beelzebul cast out demons, by whom do your sons cast them out? So they will be your judges. 20 But if I cast out demons by the finger of God, then the kingdom of God has come upon you. 21 When a strong man, fully armed, guards his own house, his possessions are undisturbed. 22 But when someone stronger than he attacks him and overpowers him, he takes away from him all his armor on which he had relied and distributes his plunder. 23 He who is not with Me is against Me; and he who does not gather with Me, scatters.
Jesus points out the obvious. Satan isn’t going to undermine himself. Jesus is going good for these people, helping them out of darkness and despair. Those aren’t the end results the devil wants.
Christ also points out that some of the children of the Pharisees are exorcists and asks essentially why they would attribute His good works to the devil and not include the same works committed by their own kids. (See the aforementioned willful unbelief.) As such, their children’s good works would be a testimony against them.
So, He concludes that if His works are not from the devil, but from God, then they need to realize that the Kingdom of God is upon them. The King is here.
And the King is moving against the kingdom of this world. He is working on delivering men and women from the culture and kingdom of this world. He is helping men and women, and by His example, He is a light in a culture of darkness, that would inspire others to follow Him.
He ends with a call to the Pharisees that they can either join Him or be against Him. But if His works are from God, then they would be working against the very God they claimed to love and reverence.