A couple notes on George Yip, in his article The Contour of a Post-Postmodern Missiology.
Polythetic is defined as “Relating to or sharing a number of characteristics which occur commonly in members of a group or class, but none of which is essential for membership of that group or class.” Monothetic contextualization assumed that there was such a thing as, for instance, “Arab Culture,” and didn’t make room for diversity. Therefore, in contextualization, one would contextualize to “Arab culture.” But this approach had many problems:
For example, missionaries and missiologists have tried to create the myth that there is a Japanese culture which is homogeneous, that because of Japanese collectivism and their preference for uniformity there is a core of culture and worldview shared by the Japanese. In reality this is far from the truth. Japanese society is, and probably has always been, a society of diversity. Some thirty years ago when I went to Japan as a missionary church-planter I noticed that missionaries did church-planting in many diverse ways, each with a certain degree of success. Many learned the language and culture and tried to contextualize the gospel and plant an indigenous church according to what they perceived to be the Japanese culture. Then there were a few missionaries who did not learn the language well, used English in church-planting, and planted churches similar to American churches. They were able to attract some Japanese, showing that within the Japanese nation there were people who found cultural affinity with the Americans. This example shows that Japan needs many kinds of contextualized churches, including even a non-contextualized form of church. In a society with large intra-cultural variations, polythetic contextualization is more effective than monothetic contextualization. (408-9)
Progressive contextualization seeks to deal with the exceptions and variations within a culture:
There are many methods of Muslim evangelism and many approaches of Muslim contextualization, including the controversial insider movement. All [Yip should say many!] these are based on the assumption that there is a homogeneous and coherent Muslim culture, an assumption that is far from the truth. Both defenders and opponents of the insider movement stand on this faulty assumption. A way out is to use progressive contextualization to study specific cases of insider movements. A number of questions need to be answered. In a context where there is an insider movement, what are the specific culture, structure, and history of that group? What is this situation of power (both hidden and manifested) in that group? The answers to such questions may yield the real cause of the movement, and that may not be the maintenance of Muslim identity. This will help us to make assessments both theologically and pragmatically. (409 Emphasis mine)
I think this is helpful for shedding light on the variations of MBB experiences with “Islam.” Some see it as a form of spiritual bondage, some just as a culture/politic, and some in-between. For instance, see my article on The Complexity of Insiderness. Also note what L.D. Waterman says:
In the Bridging the Divide network, through numerous case studies from scholar-practitioners with a wide range of perspectives and experiences, we have learned of the incredible diversity of contexts within “the Muslim world.” We have noted not only differences of social and political contexts, but also of diverse spiritual alignments and experiences among Muslims. Within these very different contexts, God is working in a variety of creative ways to shine the light of the gospel.
See also: The Essentialist Fallacy.