The question, whether individual books belong to the authors to whom they were attached, must be distinguished from the other, whether they belong in the canon on the same or dissimilar terms. The canonical nature of the writing remains the same regardless of whether it is proved that it is not from the author to whom it has been ascribed.
~~Friedrich Schleiermacher (1768-1834); from Einleitung, 30 (cited in Baird, History of New Testament Research [1:213]).
In my estimation, conservatives will not like this quote because it leaves the door open for the books of the NT to have not been written by those that tradition or the books themselves claim as authors. Modern liberals will not find much too much to like here either since Schleiermacher appears to be defending the uniqueness of the canon.
I, however, like this quote quite a bit. It leaves me with the option of examining the evidence presented in the Bible itself honestly and it allows room for the inspiration of the Bible to extend past the people who wrote the words of the Bible. I like to think that the inspiration of the Bible can be seen in its authors, its words, its transmission, canonizing process, and reception. The work of the Holy Spirit did not stop when the authors of the Bible put their pens down; but it continued and continues still today.
I am as convinced today as I ever have been that the Bible is a human book, written with human hands, dealing with human problems, transmitted by human scribes, selected for the canon by humans over a long period of time, and received today by human ears and minds. However, I trust the God who is revealed in the Bible to communicate his word to us despite all of these human hands in the proverbial honey pot.
To put it a different way: the Bible is like any other ancient book, but the God that it reveals is like no other; thus, the Bible is quite unique! Can this be proven? Not at all! That's where faith comes in after all.