Jim Hamilton has proposed a center not only of OT Theology, not only of NT Theology, but of Biblical Theology, namely, the glory of God in salvation through judgment.
I think Hamilton is right on this score. What's interesting--and sad--is that after surveying the countless proposals of "centers" for biblical theology in the academic literature, he is forced to conclude: "I cannot claim to have read everything, but I am unaware of any proposal that explicitly makes the glory of God the center of biblical theology."
Here are a few brief notes to show his methodology and conclusion:
Definition of "the center of biblical theology": "In this study the center of biblical theology is defined as the concept to which the biblical authors point as the ultimate reason God creates, enters into relationship with his image-bearers, judges them when they do wrong, saves them by his mercy, and renews the creation at the consummation of history. Moreover, the center of biblical theology is the theme which all of the Bible’s other themes serve to exposit."
Methodology: "If one of the Bible’s themes is presented as the ultimate reason for all that God does, and if this theme is not only an unstated presupposition of the biblical authors but also the stated explanation they give to justify the ways of God to men, then we would seem to have a plausible center of the Bible’s theology."
Conclusion: "In summary, in view of the indications in the Bible that God intends to get glory for himself, I cannot see how any theme could be either more primal or more ultimate than the glory of God. If we can discern what God intends to accomplish from what the Bible indicates that he will accomplish, then the conclusion presses itself upon us that God intended to make himself known in all his splendor and in all his capacities—from the kindness of being a merciful savior to the severity of being a holy judge (cf. Rom 11:22)."
You can read the whole article here. You can also see how Hamilton fleshes out this theme in more detail in the book of Acts.
