...."We have the hymn presumably because the people who compiled the hymnal think it’s a good hymn–which it is. The Church has always had the habit of taking the best of whatever we humans come up with and pressing it into the worship of God. It has never been afraid to borrow from Protestants..."
Should threaten to undo us,
We will not fear, for God hath willed
His truth to triumph thru us.
The prince of darkness grim --
We tremble not for him;
His rage we can endure,
For lo! his doom is sure --
One little word shall fell him.
I find the irony here being that Luther spent the majority of his life arguing Satan controlled the papacy.
From a commenter on Mark Shea's blog:
"Speaking of theologically dubious things, when one looks at A Mighty Fortress as it is written by Luther, you see a hymn about how Christ is our defense (fortress) against the powers of sin, death, and the devil. Yet the version of A Mighty Fortress in my Catholic hymnal has thoroughly cleansed this underlining thematic material. No mention of sin or the diabolical. That is, the hymn is much more properly Catholic in its original Lutheran version, and dubiously so in the watered down ‘Catholic’ version that made the hymnal in my parish. Weird, no?"
No, that makes sense to me.
This is an interesting link: "A Mighty Fortress Is Our God": Hymns As Poetry