Looking for a Ship

Here’s a bit of a thought from the Gospel according to St. Mark, Chapter 9:

³³And he came to Capernaum: and being in the house he asked them, What was it that ye disputed among yourselves by the way?

³⁴But they held their peace: for by the way they had disputed among themselves, who should be the greatest…….

³⁸And John answered him, saying, Master, we saw one casting out devils in thy name, and he followeth not us: and we forbad him, because he followeth not us.

³⁹But Jesus said, Forbid him not: for there is no man which shall do a miracle in my name, that can lightly speak evil of me.

⁴⁰For he that is not against us is on our part.

St. Augustine, de Con. Evan., 4, 5: We must take care that this saying of the Lord       appear not to be contrary to that where He says, “He who is not with Me is against Me.” [Luke 11:23] Or will any one say that the difference lies in that here He says to His disciples, “For he that is not against you is on your part,” but in the other He speaks of Himself, “He who is not with Me is against Me?” As if indeed it were possible [ed. note: St. Augustine has here quasi vero, instead of quasi non, which hardly makes sense; the latter reading has also been found in an old edition of the Catena Aurea, A.D. 1417.] that he who is joined to Christ’s disciples, who are     as His members, should not be with Him.

How if it were so, could it be true that “he that receiveth you receiveth Me?”  [Matt. 10:40] Or how is he not against Him who is against His disciples? Where then       will be that saying, “He who despiseth you, despiseth Me? [Luke 10:16] But surely   what is implied is that a man is not with Him in as far as he is against Him, and is not against Him in as far as he is with Him.

For instance, he who worked miracles in the name of Christ, and yet did not join       himself to the body of His disciples, in as far as he worked the miracles in His       name, was with them, and was not against them; again, in that he did not join their     society, he was not with them, and was against them.

And, so, why are there are two or more “one, true Churches” who take delight in skewering the others?  Are we able ask for or, worse, to set limits on the operation of God’s grace?  Can we confine the work of the Holy Spirit within a particular ecclesiological structure?