From an interview with Greg Beale:

If you’re going to do grammatical-historical exegesis of the Old Testament one of the first things you must do—whether you’re a higher critic, a non-conservative, or a conservative—is recognize that the Old Testament writers understood that they were under divine inspiration. If you’re going to do this sort of exegesis you’ve got to include that. Too many people fail to do this. How would this realization effect our understanding of an Old Testament authors’ intention? Would an Old Testament author say “What I’m saying here should just be narrowly understand in this narrow historical context”? Or, would the Old Testament author allow that his intention is thicker and larger than even he understood it because he believed he was writing under divine inspiration?

Perhaps an illustration would help. If I were to have a student over to my house and I said “Ah, there’s nothing I enjoy more in the summer than sitting on the patio, sipping lemonade, and listening to Bach.” Now, if that student comes to you and says “Hey, I was over at Beale’s house and he says that he really enjoys sipping lemonade and listening to Bach.” And then you ask, “Well, does he like other composers like Vivaldi? Does he like Pachabel?” The answer to that would be “Yes,” because I’m really just referring to Bach as a part for a whole. There is more in my intention, which is very thick. Now, if you asked, “Does he like hard rock like Carl Trueman does?” the answer would be “No,” because that is outside of what I would call my “peripheral intention.” Even though I did not have Vivaldi and Pachabel in my narrow intention when I spoke, it would be correct to think that they are a part of my wider attention.

So we’re not so much talking about a state of mind but what clues are in the text. I don’t think I’m guilty of making the authorial fallacy—we’re concerned about what evidence the text gives as to what was intended by the author. What the illustration gets at is that intentions can be much “thicker” and need to be unpacked, even when someone is speaking or writing who is not divinely inspired – how much more would this be the case for an inspired writer. Thus, it is legitimate in a grammatical-historical way to pursue this. I would say if you’re going to do grammatical-historical exegesis you must recognize that the Old Testament authors considered themselves inspired and you must take that into consideration. Most people don’t do this in their grammatical-historical exegesis, so in some ways I’m redefining the concept because I think it is too narrowly defined by too many people. Vern Poythress has written quite a bit about this particular topic, and I would direct readers to some of his works.

You can read the whole, wide-ranging interview here.