I’ve said that reversion takes two forms. The first is the meaning I think that the organizers of the conference on ex-Mennonites have in mind: One might leave the church of one’s parents, but remain a Christian in one’s general worldview. The second is the way that I think of it missiologically: One might leave the religion of one’s parents, meaning that one becomes non-Christian.
Who then is likely to revert (in either sense)? When people think of the church in Zimbabwe, they might think that we are looking for someone who leaves a traditional religion (such as the worship of Mwari vaMatonjeni at the shrines in the Matopo Hills) for Christian faith. Then after trying Christianity he/she might return to the traditional religion.
I suspect that this is the less typical case. More typically (I suspect) the one who reverts is the child or grandchild of Christians, and then rediscovers some form of the traditional religion renewed for today. Similarly in Canada, I suspect that those from a Christian background who “revert” and embrace some form of First Nations spirituality are not themselves first generation converts.
What happens is similar to what happened when their grandparents first converted. The religious worldview answers their grandparents learned from their parents were inadequate for new challenges. Similarly, the answers that they now have are inadequate. Why they are inadequate belongs in the next blog.
When we think of those who leave the church they grew up in, but remain Christian, I suspect a similar dynamic is at work. The Brethren in Christ (BIC) of my youth had a strong group identity which tended to keep members in the church, even when they moved to a part of the country where the BIC were not. One of the ways that we exerted pressure to keep people in the group was through the use of boundary behaviour. We were separate from the world, and we used clear markers to maintain our separation.
So my mother wore a covering until I was 15 years old, and my father wore a plain vest with no tie. Over time, as one generation learned from their parents how to live, the patterns we learned (represented by but not limited to these boundary behaviours), came to be seen as irrelevant.
So those who leave the church of their youth, while remaining generally Christian, are generally not those who paid the price to become part of the church. My maternal grandmother, for example, came from a Lutheran background. Becoming BIC meant that she had to embrace the plain dress and give up the fine clothes and jewelry enjoyed in her life before belonging to the BIC. It is unlikely that, having made that choice, she would go back on it. But the same issues are experienced quite differently in the lives of her children and grandchildren (and so on).
To some extent, the choice that someone from the new generation makes to leave is a kind of conversion, embracing a new worldview, with new religious commitments.
 Missiological research suggests that, if the theological process is not fully contextualized, the fourth generation after first contact with Christian mission will become nominal in its faith, and is ripe for either secularization or embracing a revitalisation of the traditional religion. I do not have a reference here, but simply my memory from missiological studies.