A Community of Outsiders
There are several textual elements that are important for interpreting the exorcism of the Gerasene demoniac. I will highlight two; one is significant for what I believe is the main thrust of the pericope, and the other is more playful and shows Luke’s sense of humor and irony. Playful first.
When Jesus is approached by the demoniac—and it seems the man seeks Jesus out, intercepting him stepping out of the boat—the demons do not immediately obey Jesus’ command. The exchange is really quite ridiculous. The demon-possessed man seeks Jesus out; apparently he has taken it upon himself to guard the coast. The first words that Luke quotes are from the demoniac, bemoaning that Jesus is tormenting the demons! Only then does Luke tell the reader, almost as an aside, “for Jesus had commanded the unclean spirit to come out of the man” (v 29a NRSV). So the demons approach Jesus and then immediately accuse Jesus of tormenting them (meanwhile we are told that the demons have in fact been tormenting the man they’ve possessed [v 29b]).
After Jesus gets a name out of the demons, they make a request. They ask him not to send them back to the abyss (v 31). Here is where the humorous narration turns ironic. The Greek word for “abyss”—abussos— has several referents. It means depth or abyss but is also used in the Greek translation of the Old Testament (the Septuagint) for “the pit” (Sheol, the place of the dead) and in Genesis 1:2 for “the deep” or the dangerous, formlessly void waters. Abussos has connotations of the uncontrollable waters, which is a common symbol of fear and disorder in ancient near eastern cultures.
What is ironic is that after the demons beg Jesus not to send them back the the abussos, the uncontrollable waters of the deep, and barter the pigs as an alternative, the possessed pigs run out into the lake anyway (v 33)! Luke paints the picture that this legion of demons is fickle and self-defeating. They end up in the very abbusos they had sought to avoid!
The second textual element is more globally significant, and will develop into what I believe is the main thrust of the passage. Jesus takes a boat across the Sea of Galilee and arrives, we are told, in Gerasa—the “country of the Gerasenes” (v 26). As many commentators note, this is muddled geography, for Gerasa does not border the sea at all but is almost forty miles Southeast. Luke draws on Mark’s telling here, and as William Placher notes this geographical manipulation serves a political point. Gerasa was the site of a massacre by the Romans around the 6os, when Mark was writing his Gospel. Consequently, this passage’s use of location is subversive. (I wish I could discuss this more! But for more on the political and military allusions, see Placher’s Luke and, for even more extended discussion, Ched Meyers, Binding the Strong Man.)
More broadly, however, Gerasa is definitely Gentile territory. Jesus sets foot into Gentile land and is immediately confronted with the most unclean, uncontrollable, and ungodly of persons. This is the kind of person that would reinforce the Jewish disdain of Gentiles. See, they might think, these Gentiles really are a godforsaken people. And Jesus, as a proper Jew, should not be interacting with him, at least to remain in good standing. But where there should be boundaries—dividing clean from unclean, pure from impure, Jew from Gentile—Jesus creates communion. And this encounter is a sign of the central boundary in Jesus’ culture being overcome.
Jesus cleanses the man—this Gentile, Gerasene demoniac. Whereas in general Jesus does not permit those he heals to tell of it, with this man he makes an exception. Here we have a great reversal. The Church is that body of people who is commissioned to be Christ’s witnesses (Acts 1:8), and a Gentile—a Gentile and not a Jew!—is the first member, the first person commissioned to bear witness to Christ’s new work.
Because we think that those of us Christians who are Gentiles (which is most of us, by the way) have rights to God’s promises, we don’t recognize how scandalous this reversal is. However, God’s election was always of the Jews first—they are the people of promise through whom all nations will be blessed. Christ’s ministry—and the community he creates in his resurrection—is scandalous because he engrafts Gentiles (us!) into the life of his chosen people. Outsiders have now received the blessing of sharing in God’s holy people.
Becoming faithful witnesses of God requires sharing in Christ’s reversals—becoming a community of outsiders. And this is not because “we” can include “them.” Rather, we are already outsiders who only by God’s gracious action in Christ have been sent as witnesses. In Christ’s new kingdom, the last (this Gentile) will be first (a part of God’s new people). Who do we now treat or see as “last” or as “outside”? Who do we bind and chain with the hopes of abating their unruly and uncontrollable presence? Might they be sites of new life, of the reversal that is the signature of Christ’s in-breaking kingdom  William C Placher, Mark: Belief: A Theological Commentary on the Bible (Louisville: Westminster John Knox, 2010), 80-1.  Ched Meyers, Binding the Strong Man: A Political Reading of Mark’s Story of Jesus (Maryknoll: Orbis, 1988, 2008).