How can Satan drive out Satan?

The scribes who had come from Jerusalem said of Jesus,
"He is possessed by Beelzebul," and
"By the prince of demons he drives out demons."
Summoning them, he began to speak to them in parables,
"How can Satan drive out Satan?
If a kingdom is divided against itself, that kingdom cannot stand.
And if a house is divided against itself,
that house will not be able to stand.
And if Satan has risen up against himself and is divided,
he cannot stand;
that is the end of him.
But no one can enter a strong man's house to plunder his property
unless he first ties up the strong man.
Then he can plunder his house.
Amen, I say to you, all sins and all blasphemies
that people utter will be forgiven them.
But whoever blasphemes against the Holy Spirit
will never have forgiveness,
but is guilty of an everlasting sin."
For they had said, "He has an unclean spirit."
(Mk 3:22-30)