I don’t know the proper term for this, but does a nihil obstat or imprimatur ever “expire”?
I have purchased a number of 19th-century Catholic books from estate auctions and antique stores. Most are prayer manuals, guides to popular devotions, and lives of the saints; most of that material is historical and fixed. But some are more theological, and some are catechisms. They were, of course, written before the changes in practice that came from Vatican II, before the current Catechism, and before the 20th-century revisions of the Code of Canon Law. However, most of them have a nihil obstat and imprimatur from the bishop at the time of publication.
I know that an imprimatur is no guarantee of infallability, and it’s pretty obvious that when the book refers to the Austrian empire or somesuch that I have to translate that to modern political reality, so I do read with my common sense turned on. Guess what I’m asking is, what “weight” does a nihil obstat or imprimatur add to a book? Should it be ignored after a certain point? Does it just indicate that the work is doctrinally sound only at the time of publication? Since doctine does not change, are they “good” forever?
I know, this is probably a question for a lengthy treatise, and I’m expecting a one paragraph response. I appreciate any direction you can provide.