Luther thought if a book preaches justification by faith strongly it is inspired. But that Professor did say that if there were a providentially protected teaching authority, that would settle it. He did not believe there is such a thing. We know there is, as our apologetics shows easily. A sad case of that emerged in a book by Gerhard Maier, The End of the Historical Critical Method , published by the great Lutheran house at Concordia, in 1974.
Scripture considers itself as revelation.
This is a shocker, a perfect case of lifting self by the shoelaces. Scripture cannot prove Scripture is inspired until we know Scripture is itself inspired. And it definitely does not say it is inspired. Nor does it say Scripture is the only way in which God communicates to us. The article just mentioned was published in The Biblical World 37, pp.