Jesus did not ask because He needed the information. Matthew Henry says Christ could name every fallen spirit, "but he demands this, that the standers by might be affected with the vast numbers and power of those malignant infernal spirits." The question brought into the open how deep the man's bondage went. It also helps explain what Mark had already described: why chains could not hold him and why "neither could any man tame him" (Mark 5:4). The Greek verb for "asked" is in a tense that can describe ongoing action, so the asking may have been more than a single word.

The answer came: "My name is Legion: for we are many" (Mark 5:9). The reply moves from "my" to "we," one voice speaking for many. Luke explains, "because many devils were entered into him" (Luke 8:30). The spirits then "besought him much that he would not send them away out of the country" and asked to go into the swine (Mark 5:10-12). "Forthwith Jesus gave them leave," and the herd of about two thousand ran into the sea (Mark 5:13).

A legion was a unit of the Roman army. Thayer notes that its size changed over time and that in the days of Augustus it seems to have numbered about 6,826 men, foot soldiers and horsemen together. Gill likewise says a Roman legion at first held three thousand foot soldiers and three hundred horsemen, and later six thousand foot and six hundred horse. The word legion appears only four times in the New Testament: here, Mark 5:15, Luke 8:30, and Matthew 26:53, where Jesus says His Father could give Him "more than twelve legions of angels."

The man's own name is never given. In Mark 5:15 he is simply "him that was possessed with the devil, and had the legion."

This question shows Jesus' authority over a multitude of evil. The spirits called themselves many, yet they could only beg. Matthew Henry writes, "They are many devils, and yet but one legion engaged in the same wicked cause." Their numbers did not change the outcome. They could not even enter the swine until Jesus "gave them leave" (Mark 5:13).

The question also prepares for the man's new identity. The spirits gave their name; the man, once freed, needed none of it. He is found "sitting, and clothed, and in his right mind" and is sent home to tell "how great things the Lord hath done for thee" (Mark 5:15, 19).