Jesus stated in Matthew 12:25 that a kingdom divided against itself cannot stand. It is a general principle that division leads to destruction. Such is true in the family, the church (cf. I Cor. 1:10-13), and also the spiritual realm.
If what the Pharisees stated was true, then Satan was defeating himself by casting out himself! It is illogical to think that Satan would work against his very purpose--that is, to have control over man and his mind. Why would Satan rob himself of his greatest achievement? Jesus isn't saying that Satan could not do this, but that he would not. It should be noted that if the Pharisees' claim was true (which it wasn't), then they should have been pleased at Satan's self-destruction! It is implied, however, that they don't truly believe their claim themselves since they were not pleased with Jesus' actions here.
Jesus asked a question related to their consistency in Matthew 12:27. Some disciples (i.e., "sons") of the Pharisees evidently made claims about their ability to cast out demons (e.g., Acts 19:13-20). Jesus is not giving authenticity to the claims, but He does use them to create a dilemma. Essentially, Jesus is saying: "Your disciples claim the ability to cast out demons. Now, whose power do they work by--God's or Satan's?" This was a dilemma because if they say by Satan's power, then they're condemning themselves since these alleged exorcists were their disciples, but if they say by God's power, then the crowd would want to know why they think Jesus' power is from a different source. Either way they answer this question, they are trapped!
Jesus wanted the Pharisees to draw the logical conclusion that He casts "out demons by the Spirit of God" (i.e., the power of the Holy Spirit). To be reasonable, they must admit that Satan would not cast out demons, thereby destroying himself, and certainly their own "exorcists" would not work by the power of the devil. Those with good and honest hearts would come to the correct understanding--Jesus was working by God's power and was not working with Satan in any way. This great miracle He had just performed was a testimony to the truth that the kingdom of God was exceedingly near. The King would soon establish His kingdom!
Jesus asked this question in Matthew 12:29 - "How can one enter a strong man's house and plunder his goods, unless he first binds the strong man?" In this context, Satan is the "strong man", the body of the demon-possessed man is the "strong man's house", and the man himself, while under Satan's possession, could rightly be called one of his "goods". Jesus had "entered" Satan's house and "robbed" him of his goods; that is, Jesus overpowered Satan by coming into his territory and taking by force that which Satan claimed as his own (namely, the possessed man). Our Lord's point here is that He must be stronger than Satan in order to cast him out. Thus, He is not in league with Satan; He is superior to him! It should be noted that Satan is depicted as being "strong" (cf. I Pet. 5:8). However, although he is powerful, his power is not unlimited (cf. Jam. 4:7). He is no match for a faithful child of God who resists him!
Jesus then declared in Matthew 12:30 - "He who is not with Me is against Me". This point emphasized to the scribes, Pharisees, and bystanders that there was (and is) no middle ground. If one is not with Christ, then he is against Him. Either the religious leaders would accept Him and His miraculous power from the Holy Spirit and be an asset to Him, or they would reject Him and hinder His work for no good reason. Sadly, because of their selfish jealousy and hard hearts, they would choose to do the latter.
We will continue studying this narrative tomorrow.