I find it interesting that Luke would begin Jesus’ ministry with a miracle that casts out a demon. Why do that? It is the first miracle performed by Jesus in both Luke (Luke 4:31-36) and Mark (cf. Mark 1:21-27). Matthew mentions this only generally (Matthew 4:23-25), but John begins Jesus public ministry with the miracle of changing water into wine (John 2:1-11). The accounts end with the astonishment of the people (the Synoptics) and the belief of the disciples (John). What can we make of these things?
Both Luke and Mark tell us that the demoniacs knew who Jesus was, but Jesus silenced them (Mark 1:23-25; Luke 4:33-35). How did they know him? The Greek verb used by Luke is oida (G1492; also eido), which means knowing by understanding or perception. It is different from the Greek ginosko (G1096), and ginosko comes to know by experience (cf. Luke 8:10), while oida has to do with what one knows intuitively or perceives automatically (cf. Luke 11:13). So, the demoniacs whom Jesus healed knew him intuitively (Luke 4:34, 41; Mark 1:25, 34). Mark 3:11 says that when they saw (G2334 – theoreo) him they recognized him. That is, they didn’t need to come to know him by association.
I have already discussed the idea of demons in previous studies, so I don’t wish to repeat those studies here, but suffice it to say that I do not believe they are evil sentient spirit beings, but rather problems within men’s spirits that possess them. It could be a bad habit or an addiction brought on by chemicals (alcohol or drugs), a demon could even be a sickness, especially those dealing with psychological problems. However the phenomena can be defined, the demon is not a sentient spirit being that takes possession of a human being. Some Christians will find it difficult to agree to this, but most of us can agree that no matter what a demon is, Jesus had supreme authority over it, and the demon was forced to obey Jesus (and later Jesus’ disciples).
According to the Septuagint, the Greek word demon (daimonion – G1140) is found in eight places in the Old Testament. According to Deuteronomy 32:17, demons were worshiped as gods, but they were recent gods. Israel’s ancient ancestors didn’t know or fear them. Psalm 96:5 claims that all the gods of the nations were demons! If we compare this with Deuteronomy 32:17, those gods were recent gods, who were not known in earlier history. The Scriptures don’t claim that every demon was a god, but it does claim that all the false gods of the nations (gentiles) were demons.
Psalm 106:37 says that Israel sacrificed their sons and daughters to demons, and Isaiah 65:3 claims that these demons weren’t living. They didn’t exist in ancient times (Deuteronomy 32:17), but lived later. Nevertheless, by the time of Isaiah the gods, demons, of the nations were no longer living in the days of Isaiah’s prophecy(Isaiah 65:3).
Psalm 82 shows that men who lead the people or have authority over a nation or part of that nation are called gods (cf. Psalm 82:1, 6-7). They receive their authority ultimately from God, the Almighty or Supreme Authority. If we compare Psalm 82 with Psalm 96:5 we find that the demons who were the gods of the gentiles were once the kings of those nations, but by the time of Isaiah they were all dead. In other words, these demons were men who had power over other men. They ruled the gentiles from the grave in Isaiah’s day, because they no longer existed!
Psalm 91:6 unveils a different demon. There, the author associates the demon of destruction with pestilence, or a disease that is able to take control (authority) over the body of a man. Isaiah 13:21, 34:13 and 65:11 (in the Septuagint) seem to point to wild men living in the desert whose right reasoning has left them, and they engage in weird religious practices. Luke, also, associates demon possession with disease in Luke 4:41-42, and psychological problems (Luke 4:33-34). Nevertheless, the Scriptures never show that the demon spirit is a sentient being (fallen angel), as has been traditionally believed by many in the Church.
The demoniac in Luke 4:33 may even have been a leader in the synagogue, but this cannot be proved. Nevertheless, he was in the synagogue, and normally known demoniacs were not admitted there. So, whatever the circumstance for his presence, he challenged Jesus, claiming that even though he was the Messiah, Jesus had nothing in common with the people. The demoniac claimed Jesus would harm them, ultimately destroying the nation by claiming to be the Messiah (Luke 4:33-34). Yet, it was the demon that was destroying the person it possessed (Luke 4:41-42), just as addiction to alcohol or drugs destroys the ones they possess.
 See my earlier studies on the subject of evil spirits and spiritism on my main blogsite, Smoodock Blog: Who or What Are Demons; Demons ~ Corrupt Spiritualism; and Demons ~ Personification or Living Beings. Another contextual study from Luke 11 would be: Demons and Dry Places. Other more specific studies can be found by reading A Demon Called Legion; Balaam and the Witch of Endor; and Simon the Sorcerer and the Soothsayer.
 They are Deuteronomy 32:17; Psalm 91:6; 96:5; 106:37; Isaiah 13:21; 34:13; 65:3, 11.
 If they lived later, that is, weren’t in existence during ancient times, they couldn’t be fallen angels, which some traditions hold them to be.
 A person who assumes the persona of a hero or an admired leader might be considered possessed by that persona—much like a modern actor who is really “into” his part. The demoniac in Capernaum, if, indeed, he was a leader in the synagogue, could have given himself over to act in the steps of an admired hero of Judaism, whose presence the man longed to continue to make known. If this is true, the demoniac never really becomes the person he was meant to be, because he is compelled to act in the manner he presumes his hero would act. Theoretically, in the context of possession the demoniac sooner or later begins to automatically act out its assumed persona, and can no longer allow the real persona of the man to mature.