I have found an article that makes an extremely important point for the types of conversations that crop up at SI, regarding who or what is a fundamentalist. Interlocutors here at SI tend to define religious communities by their beliefs. So, a person is Fundamentalist if he or she believes (insert content). Although there is some value there, I think much more appropriate are the kinds of definition and measurement that come from historical affiliation. That is, a person is a Fundamentalist if he or she belongs to the network of Fundamentalist institutions/affiliations. This sort of approach is necessary to discuss persons as social groups, rather than as merely statistically grouped individuals.
http://blogs.ssrc.org/tif/2008/08/29/the-measurement-of-evangelicals/
