What does Mark 3:23 mean?

Matthew 12:24–25 indicates that the scribes from Jerusalem are present in the crowd. Like their local counterparts, they use an oblique attack (Mark 2:16). Their goal is to convince the people to stop following Jesus, claiming He performs miracles under Satan's authority. Jesus uses a parable to show how faulty their reasoning is.

"Parable" is from the Greek root word parabole. It refers to something placed next to something else as a comparison. All of Jesus' teachings in Mark 2 use parable to some degree (Mark 2:16–17, 19–22) even when the included story is true (Mark 2:25–26) or His very act of healing becomes the metaphor for forgiveness of sins (Mark 2:5–12). Mark 4:34 says that Jesus' public teaching is all in parables, but He explains the deeper message to His disciples in private.

The scribes infer that lesser demons have possessed people in a way that somehow displeases Satan, and Satan uses Jesus to cast them out. Or that the entire incident is just a show meant to fool the people. Jesus explains that everything the demons do is under Satan's direction, and to cast out a lesser demon is to cast out Satan.

The Bible doesn't go into great detail about Satan and the other demons. We know that when Satan rebelled against God, one-third of the angels followed him into exile (Revelation 12:3–9). The demons have some kind of a hierarchy—the greater ones are called princes (Daniel 10). But the Bible doesn't tell us why or how demons possess people. Everything they do is for Satan's evil purpose, however, and to cast them out would work against his plan.