Graeme Goldsworthy on the unity of the Bible:
The unity of the Bible is matter of biblical revelation, not of empirical investigation. Put simply, I believe that the Bible gives me a single, accurate, and coherent picture of reality principally because Jesus tells me that it does. The unity of the Bible is an article of faith before ever it is arrived at empirically. The empirical discovery of the unity is governed by the presupposition of divine revelation. If I have difficulty in understanding how that unity exists in the face of certain phenomena, or apparent phenomena, that is a problem in my understanding, not in the biblical text.
Jojo Agot 