I am continuing to study through Isaiah with Brevard Childs Isaiah from the Old Testament Library, and I found another quote I want to share with a very brief comment. In discussing the literary connections between chapter 34 and 2nd/3rd Isaiah, he says:
. . . For example, are the vocabulary affinities between chapter 34 and 40-66 to be given precedence over the large number of words in chapter 34 that are not found in chapters 40-66? Or again, what role does one assign to apparent similarities of syntax and style? — p. 253
Now this quote seems very simple, but it embodies an important principle in Bible study, in areas ranging from comparing one scripture to another all the way to serious application of various critical methodologies. The principle is this: Differences and similarities must both be considered in any comparison.
One of the best illustrations of this idea comes from the history of comparing the Babylonian creation story to Genesis 1. At first, there was a mass acceptance of the idea that Genesis was essentially copied from the Babylonian story. There are, indeed, many points of contact between the two. Then there was a reaction indicating that Genesis was almost totally different. There are also, it is true, substantial differences. After a time, most scholars came to the conclusion that there was a relationship, but that it was not a direct literary relationship. They concluded that both likely went back to an earlier source which each had used in its own way. (This is a very generalized history, and much of the conflict still goes on, especially in Christian apologetics.)
I’d recommend getting a copy of each and enumerating key points and then lining them up together. What is the same? What appears to be related but is not identical? What is completely different? (Pritchard’s Ancient Near Eastern Texts Relating to the Old Testament with Supplement is a good source and is probably available at any good college or university library.) Then compare your own lists. I do this with the creation of man in each story when I’m teaching either on Genesis or the ancient near east in general, and I find the results are always interesting.
The same principle, however, applies to comparing any two sets of material. For comparing scripture, make sure to understand both texts in their context, then look at what is similar between them but also at what is different. Just listing one or the other presents an unbalanced picture.