One thing about the gospels that is embarrassing to modernity is the prominence of demon possession. In just Mark’s gospel there are four detailed stories of Jesus performing exorcisms. It is popular today to give psychological, medical, or even political explanations for demon possession.
Not only is this offensive to modern sensibilities, but it is mystifying if you are trying to interpret the gospels from just the Old Testament. The Old Testament occasionally uses the phrase “evil spirit”, but means something different. For instance, God sent an evil spirit to torment Saul (I Samuel 16:14-16). But his people did not call for an exorcist. They called for a harpist.
Also the Old Testament spoke of pagan gods as demons (Deuteronomy 32:17). But other words for pagan gods were more usual and the gods, although they contribute to false prophecy, do not possess people the way the demons in the gospels do.
In Mind the Gap, Matthias Henze says that the only way to understand the unclean spirits and demons of the gospels is to read the Jewish literature that came into existence in the years just before Jesus.
He looks at three works, each written a century (loosely conceived) after the last.
First, is the Book of the Watchers, a part of the Enoch literature. This book expands the story from Genesis 6 about how before the Flood angels had taken human women as wives. Apparently the original sin of the Watchers was to come down to earth at all. They did not belong here. But once they came down, they produced offspring who were trapped here even in death.
The Hebrew calls the offspring of the angels and humans, nephilim. But the Greek of the Septuagint says they were giants, and that is what the Book of the Watchers called them. The Flood came and killed all life except Noah’s family. However, the giants, being half angels, could neither completely die nor return to the angelic realm. They became unclean spirits who “lead astray, do violence, make desolate, and attack and wrestle and hurl upon the earth and cause illness” (p. 105).
It is important to recognize that the Book of the Watchers is apocalyptic literature. It has the view that the unclean spirits will do what they do until the end of time when God will finally vanquish them.
Second, there is the book of Jubilees. In this book the same story gets more details and it becomes a kind of explanation for why bad things happen.
Noah prays that the spirits not be allowed to molest his grandchildren. God announces his intention to bind all the evil spirits. But their master, Mastema, appears before God and pleads that God not lock away all the spirits. It may not be good for the dark side to be completely powerless. So God has most of the demons thrown into a terrible place of judgment, but allows a tenth of them to go free.
This explains the true nature of the human condition, why life is hard, and the tragic happens. Of course, it could be ten times worse. And, again, there is apocalyptic hope. Mastema, or Satan, will be judged at the end of time.
Finally, in the first century before Christ there came to be at Qumran a document called The Songs of the Sage. The people at Qumran were very much into both angels and demons. They had formulas to curse demons, especially the chief demon, whom they called Mastema, Belial, Satan, and the Angel of Darkness.
But apparently by the time of the Songs of the Sage it was expected that the end time was very near. The sage felt that the best strategy to ward off demons was no longer to curse them, but to praise God and proclaim his radiance. When the community does this the spirits will be frightened and dismayed. They will flee and scatter. To proclaim God’s kingdom impinges upon this other kingdom.
Henze see all this as the background for Mark’s stories about Jesus casting out demons. The casting out of demons is a manifestation of the kingdom of God. It is a sign of the end time. Jesus did not destroy demons. But his presence terrified them and was a sign of the nearness of judgment.