Augustine of Hippo — as excerpted in the Catena Aurea on Luke 8:26-39

“(ubi sup.) Now that he was bound by brazen fetters and chains, signifies the harsh and severe laws of the Gentiles, by which also in their states offences are restrained. But, that having burst these chains he was driven by the evil spirit into the wilderness, means that having broken through these laws, he was also led by lust to those crimes which exceeded the ordinary life of men. By the expression that there was in him a legion of devils, the nations are signified who served many devils. But the fact that the devils were permitted to go into the swine, which fed on the mountains, signifies also the unclean and proud men over whom the evil spirits have dominion, because of their worship of idols. For the swine are they who, after the manner of unclean animals without speech and reason, have defiled the grace of their natural virtues by the filthy actions of their life.”