on appeals to consensus

Mark Goodacre has posted some thoughts on Tom Wright's "Decoding Da Vinci," and he rightly takes issue with Wright's read of the consensus regarding the date of the Gospels and the primitivity of the Gospel traditions.

But this all brings to mind several ongoing questions I've had on the common tactic of appealing to consensus.

• First, consensus is a very slippery notion. What is consensus? I wouldn't think it's unanimity, at least not in dealing with such large and diverse groups of people. And it's certainly not simple majority. So what is it? 70%? 80%? Can 90+% safely be considered consensus?
• Second, who gets to be part of the polling sample? Only those working within a particular historical or theological perspective or methodological paradigm? All those who have published scholarly monographs on the subject? All scholars who have studied the subject in depth, whether they've published on it or not? And who determines what makes a "scholar" or appropriate authority on the subject?
• Third, how does one actually go about doing the polling to assess consensus? One can meticulously search through all relevant literature on the subject and record opinions in a table (which is sometimes done on specific issues), but this then leads to some of the questions in the previous point, and one often quickly realizes that individual scholarly perspectives on any given issue are too complex to fit neatly into a simplistic table or scale.
• Finally, even if one can get past the previous questions, what does consensus prove? The consensus in 1976 on Paul's perspective on the Torah and his understanding of "justification by faith" was pretty strong, I would guess, until Ed Sanders provoked a Kuhnian paradigm shift with his Paul and Palestinian Judaism the following year. Now there is as much variegation in perspective on these issues as some of Sanders' respondents have claimed was evident in the nomism and soteriology of first century Judaism. Did the consensus prior to Sanders' book make that so-called "Lutheran" view correct? Does the lack of consensus since mean that no one has any real grasp of any of the issues?

In spite of these questions, the search for consensus is an inevitable desire, and still valuable, it seems to me. It can act as a safeguard against unreasonable idiosyncratism, so that when one recognizes one is stepping out against the overwhelming tide one should walk with great care and continued attention to the flow of scholarship in the other direction. Also, no one can study all ancillary issues him or herself when focusing on a particular topic; we rely on the judgments of others, and especially the judgment of the majority and ideally the consensus, in order to build on those judgments in making our own. But we must be cautious with appeals to consensus, as they do not deliver everything they appear to promise, and too often they act as unwieldy tools in some sort of power game, crushing our foes (at least, in our eyes) but leaving us naked and bare.

I'll close, appropriately, with some words from Tom Wright himself: "A consensus is something as rare as snow in midsummer, and no doubt similarly transitory" (Jesus and the Victory of God).

UPDATE: It appears this post has raised quite a brouhaha! For further developments, see my posts cynicism and optimism on consensus, more on consensus, hope for consensus!, and consensus, consensus, my kingdom for consensus!