Robert Morgan's classic work on the nature of New Testament Theology, including his translations of William Wrede's 'The Task and Method of "New Testament Theology"' and Adolf Schlatter's 'The Theology of the New Testament and Dogmatics'.
To clarify the title of the book, these essays do not delve into the "nature" of NT theology in any sort of total sense. The book really seeks only to account for the rise and purpose of historical criticism, and to establish the debate between "history" and "theology" as the task of the scholar. This book establishes the debate with rigor and interest, but the limited scope of the book will mean that it has a limited interest to students of theology; although I should think that all students of theology would benefit greatly by a good account of this debate and its consequences.
The first essay is essentially an introduction, by Robert Morgan, to the issues and personalities. It is, on the whole, the best essay in the book, because it summarizes the issues well and includes ideas from a wider range of contributors to these debates.
The second essay, by legendary scholar William Wrede, takes the historical critical side of the debate. In Wrede's view, the scholar must do the work of a historian, removing all presuppositions and personal commitments from the task of historical investigation into the NT. The historian must approach the task with a "disinterested concern for knowledge." Furthermore, the NT itself cannot be the limit of the investigation into early Christianity; research must take into account any and all available information, and the "canon" of the NT cannot limit the scope of investigation. Wrede concludes his essay by stating that both parts of the phrase "New Testament theology" are invalid. The phrase "New Testament" is invalid because it limits the scope of inquiry to specific dogmas of specific early Christians, and "theology" is invalid because such dogmas should not be the goal of the scholar. One is not to establish a theology "from" the NT, but only to establish the theology found "in" the NT. Rather than "theology," scholars should consider their subject the investigation of the "early Christian history of religion."
The third essay is by German theologian Adolf Schlatter. Schlatter seeks to demonstrate that, contra Wrede, the scholar is incapable of removing their presuppositions and self-interest. To be sure, certain presuppositions can get in the way of historical inquiry, and the scholar must be as objective as possible, but to remove all self-interest is a form of self-annihilation, which is not only impossible, but undesirable. In Schlatter's view, to remove dogmatics from historical inquiry is "an illusory fiction." Furthermore, Schlatter challenges the idea of de-centralizing the NT from historical research. In his view, the early Christian movement was established the way it was precisely because they centralized these particular texts, and understood all else in light of them. To try and understand the early Christian movement with a de-centralized NT is to attempt to understand that movement differently than it understood itself.
One issue with which Wrede and Schlatter seem to agree, and which I found insightful, is that exegesis of texts and documents is wrongly obsessed with the precision and over-analysis of even the most incidental and insignificant details. It's likely that NT writers were not trying to be nearly as precise with their words as we assume when we dissect their texts. This leads to all sorts of misleading ideas about the NT.
On the whole, Both Wrede's and Schlatter's essays were quite a bit longer than they needed to be, and they both went into material that was largely unnecessary to the task. Anyone not so interested in the original essays could read Morgan's introductory essay and easily get the gist. However, reading the actual work of these important early 20th century scholars has exceptional value, and I recommend it even though both essays drifted at various points.
It seems that the perspectives of both Wrede and Schlatter were largely dictated by their own personal commitments to faith and scholarship. It also appears that Schlatter was a great deal more honest about that fact, as he simply admitted that faith is the goal of the NT, and that objectivity is not only impossible, but that it gets in the way of seeing the interested commitment of the NT writers to God and to their theological subjects. Like Schlatter, I am not at all as confident as Wrede that objectivity is attainable. Having said that, there were many points at which I was sympathetic to Wrede's design on removing bias (though Schlatter also admitted that we should remove bias where we can, even as we invest in our subject in an interested way). It seems to me that we must remove bias, and be willing to follow the evidence where it leads, while also embracing the idea that allowing our research to extend from our own experience can actually help us to see with eyes conditioned by God for good reasons. Rather than annihilate the self, God has made us to be precisely who we are as we approach the text. Schlatter is convincing that we should embrace that as we also seek to be honest about historical data.