I have been under the impression that Christ's teaching is very much along the way of "Christ is the only path." If so, what's going on in this passage?
Luke 9:49–50 (KJV)
49 And John answered and said, Master, we saw one casting out devils in thy name; and we forbad him, because he followeth not with us.
50 And Jesus said unto him, Forbid him not: for he that is not against us is for us.
How is this mysterious individual casting out devils without being a follower of Christ, and how is Jesus implying that this mysterious fellow is an ally?