Luke Timothy Johnson on Biblical Theology

What is the unifying principle of the New Testament? Is there one? If not, is it possible to do biblical theology without distorting the text somehow? Is performing New Testament theology a legitimate task? Luke Johnson doesn’t seem to think so:

Since the canon consists of a disparate collection of writings, with both the Old Testament and New Testament forming the Christian Bible, it resists reduction to any single unifying principle imposed from without as much as it lacks any explicit unifying principle within. If it excludes by its nature any “canon within the canon,” it certainly also resists any conceptual mold that either relativizes or removes the texts themselves in all their hard particularity. The resistance applies as well to any “biblical theology.” In all its forms, biblical theology is simply another attempt to reduce the many to one by means of some abstract unifying principle, whether it is denominated salvation history or justification or liberation or kerygma or regula fidei or narrativity or existential decision. All such principles demand the selection of some texts as a priori more central and governing than others. All fit the writings themselves to frames of greater or lesser abstraction. The canon resists such attempts precisely because it is made up of multiple and irreducible writings which cannot without distortion be shaped into a static symbolic system.

Luke Timothy Johnson, Scripture and Discernment: Decision Making in the Church (Nashville: Abingdon, 1996), 37.