The setting builds suspense. Gadara and (Mark's) Gerasa were both part of the Decapolis, a primarily Gentile area with a large Jewish population (Jos. War 1.155). That tombs were unclean (for example, m. Nazir 3:5; 7:3; t. Baba Batra 1:10-11) and considered the usual haunts of demons and magic (PGM 101.1-3; Nineham 1977:153) increases the audience's suspicion that these demons are inordinately powerful-hence the narrative's opening suspense and christological impact.
Even Demons Know Who Their Lord and Judge Is (8:28-29)
The demoniacs ran to Jesus (Mt 8:28), and the demons protested his coming to torture them (compare Test. Sol. 5:5). Jesus' presence also reduced them to entreating permission just to enter some pigs (v. 30). Yet in contrast to demons, many people remain unaware of Jesus as Lord and Judge.
The Kingdom Is "Already" As Well As "Not Yet" (8:29)
Because the King of the future age arrived in the first century, his kingdom also invaded this world in a way hidden to people but recognized by the evil one and his forces (see also Cullmann 1950:71). The demons here, believing they are free to torment people until the final day and expecting eternal torment in the day of judgment, recognize that their judge has just shown up, before the appointed time. God's ultimate intervention is yet to come, but this does not prevent us from depending on his power over the evil one in the present.
Jesus Values People More Than Animals or Property (8:30-32)
In ancient exorcism traditions, demons typically made a public scene when they departed, melodramatically indicating their protest and the exorcist's power (as in Jos. Ant. 8.48-49; Philostr. V.A. 4.20); but rarely did they make this much of a scene! Pigs can normally swim for some distance if necessary (Alexander 1980:214); given the mortality of demons in some Jewish traditions, this account may suggest that the demons were at least disabled or bound in hell. It would have made sense to the earliest Jewish hearers of this story that demons wished to enter pigs and that Jesus let the herd perish, but to the owners of the swine (in preinsurance days) the destruction of their herd meant financial loss, not just "deviled ham." The deliverance of the demoniacs mattered more to Jesus than the fate of the swine (see also Hooker 1983:39).
Most People Value Property More Than God's Deliverance (8:33-34)
Gentile wonderworkers were often "magicians," whose power others perceived as malevolent more often than not (as in Apul. Metam. 2.5, 20, 30; 3.16-18; 9.30). Ignoring the men's deliverance and focusing on the destruction of the property, the Gadarenes viewed Jesus as a magician, dangerous to their interests.
People's presuppositions are so strong that even divine miracles will not always convert them. I once debated for about seven hours with a professor in his office, providing evidence to refute his objections to Christianity and citing line after line of evidence for the truth of the Christian faith, each of which he dismissed on the basis of presuppositions. Finally exasperated, I demanded, "Would you believe in Jesus if someone were raised from the dead in front of you in his name?"
"No," he responded, "I'd say they weren't really dead."
"And you have the audacity to call me closed-minded for being a Christian?" I retorted.
We cannot, however, assume in advance who will respond to our testimony; most of us would have guessed that of all the Gadarenes, the ones least likely to respond to Jesus would be the demoniacs. As an atheist I argued vehemently against the gospel the first day I heard it, and the people who witnessed to me did not learn until a year later that I had become a Christian later that day and led ten people to Christ in the intervening year. We are responsible to sow seed everywhere and leave the harvest with God (13:3-23).