We don't have the originals of any of the books of the New Testament. ... There are places where we don’t know what the authors of the New Testament originally wrote.
This statement by Bart Ehrman is hardly controversial. Anyone who has been to seminary has (hopefully) acquired a modern edition of the Greek text in which variant readings are listed in the apparatus, along with a list of the most important manuscripts that support each reading. Obviously, scholars frequently disagree about which variant preserves the oldest form of the text. Thus, while we are pretty confident that our modern editions closely approximate the original wording of the NT, we are not and never will be absolutely certain that we know the original reading of every verse.
Based on this fact, Ehrman proceeds to suggest that the NT is not the inspired word of God:
We can demonstrate the error in this type of reasoning with a little thought experiment: suppose the autographs (original NT documents) had actually survived. Suppose that since the earliest days of the church, the NT autographs had been preserved and handed down from one generation to the next.What does it mean to say that God inspired the words of the text if we don’t have the words? Moreover, why should one think that God performed the miracle of inspiring the words in the first place if he didn’t perform the miracle of preserving the words? If he meant to give us his very words, why didn’t he make sure we received them?
Before the advent of the printing press or electronic reproduction, the vast majority of Christians would still be unable to directly access these documents. Thus, even if the autographs were preserved, the vast majority of Christians would remain dependent on fallible, handwritten copies. Furthermore, even after the invention of the printing press, the vast majority of Christians would still be unable to read the Greek words, and would thus remain dependent on various translations, all of which are incapable of perfectly reproducing the original words of the autographs.
Moreover, how could we ever know with absolute certainty that the autographs had indeed been preserved? In other words, how could we know that the documents handed down from generation to generation were the genuine autographs, and not mere copies? We could estimate the age of these manuscripts with the tools of paleography, and we could look for tell-tale signs, such as Paul’s closing signature in his own hand (see 1 Cor 16:21; Gal 6:11; Col 4:18; 2 Thess 3:17; Phil 19). At the end of the day, however, any decision on the authenticity of the documents would still be a matter of historical judgment and probability – just like the decisions we make in textual criticism. We could never reach the type of certainty that Ehrman’s brittle fundamentalism demands.
In conclusion, Ehrman's requirements for the divine inspiration of Scripture would only be satisfied if God miraculously delivered a perfect copy of the Bible to every Christian in his or her language. In other words, Ehrman is requiring Christianity to be something other than what it has always claimed to be: a religion rooted in history.
[Quotations from The Reliability of the New Testament, 14.]