Mateo 8:28

And when he was come to the other side into the country of the Gadarenes, there met him two possessed with demons, coming forth out of the tombs, exceeding fierce, so that no man could pass by that way.

Gadara was one of the ten cities of Decapolis ("ten-cities"), all but one of which were east of the Jordan river. The ensuing wonder about to be performed upon the city's most notorious derelict was well calculated to provide a sensational witness of Christ's glory throughout the entire section. Mark and Luke mention only one of these persons, the principal one. Note that neither Mark nor Luke states that there was "only one" of these men. The fact of demon possession is plain here. These were possessed not merely with one, but with many, demons. The conversation the demons carried on with Christ, their entry into the swine, and many other factors make it impossible to reconcile this situation with one in which the victim was merely "sick." Given writes thus:

When the Lord Jesus Christ had taken to himself a true body and a reasonable soul, when the word was made flesh and dwelt among men, Satan, by himself or by his servants, took possession of the bodies of men, cruelly torturing their flesh and agonizing their spirits. Nor are we prepared to say that demoniac possession has altogether ceased. We have seen men so act and heard men so speak and have been informed of such fiendish atrocity on their part, that we could account for their violent and outrageous conduct, or for their mischievous and diabolical acts, or for their horrid and blasphemous expressions, in no other way than that some demon, or the devil himself, had been permitted to take temporary possession of them.Mark 1, p. 234.">[8]