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Who’s With Me!?, Pt. 4: Following Jesus as a Fuzzy Set

January 9, 2023

by Greg Henson, CEO Kairos University; President of Sioux Falls Seminary and David Williams, Kairos Executive Partner; President of Taylor Seminary


About 12 weeks ago, we began a conversation about what it means to follow Jesus in community. Along the way, we have looked at everything from the missionary nature of God to wild geese to the importance of discernment.

About three weeks ago, we turned our attention to the fact that following Jesus in community requires an awareness of who is in that community. Our thought is…

“We need a way to understand, imagine, and gather with that community. In order to be the “hands and feet” of Jesus, the Body of Christ needs to be a body. We might argue that the Body of Christ is pretty adept at “cutting off its nose to spite its face,” especially in today’s culture. It is important, therefore, to have the conversation about how the Body of Christ might envision itself and the means by which it makes those determinations.”

In 1978, Paul Hiebert, a third-generation missionary and well-known missiologist, initiated a conversation about various ways to approach this task. Over the next 40+ years, scholars, pastors, missionaries, and followers of Jesus of all types continued to wrestle with these concepts. We are spending a bit of time reviewing the different approaches that Hiebert eventually codified in his writing. Two weeks ago, we looked at well-formed intrinsic sets (i.e., bounded sets) and last week we focused on well-formed extrinsic sets (i.e., centered sets). Both of these approaches favor clearly defined boundaries. In practice, this means they favor binary approaches to categorization. Today we look at fuzzy sets which do not have clear boundaries (i.e., they are not binary in nature).

Very few within the theological, missiological, and ecclesiological conversations around Hiebert’s social set theory have spent much time addressing fuzzy sets. This could be because Hiebert himself didn’t spend much time reflecting on it in his writing, and he had a clear affinity for centered set approaches to envisioning Christian community. It could also be because the fuzzy set category pushes against our propensity for binary classifications in western cultures.

As we have in our two previous posts on social set theory, let’s begin by looking at a succinct summary of Hiebert’s fuzzy set theory provided in a paper titled, “Understanding Christian Identity in Terms of Bounded and Centered Set Theory in the Writings of Paul G. Hiebert.” It was co-authored by Michael Yoder, Michael Lee, Jonathan Ro, and Robert Priest. In that essay, they offered the following summary:

Intrinsic fuzzy sets

  • Categories assume continuums and are not based on sharply divided either-or thinking
  • Objects may simultaneously belong to two or more sets – no excluded middle
  • Change is a process, not a point

Extrinsic fuzzy sets

  • Membership in a category is based on relationship to other things
  • The boundary is fuzzy with no sharp point of transition between one and the other
  • Membership is one of degrees; varying distances exist from center
  • Change or conversion is a process, not an instantaneous about-face

In case you missed it, the most prevalent feature of fuzzy sets is that there is no sharp point of transition. In practice, that means something or someone could be in two sets at the same time. For example, a color could be 30% red and 70% orange. It is neither red nor orange but both at the same time. Hiebert provided examples such as a mountain giving way to the plain or night becoming day. Both are gradual transitions. In a fuzzy set approach, a person could be both Christian and Hindu (which might be an intrinsic fuzzy set) or young and old (which might be an extrinsic fuzzy set). The point is that fuzzy sets exist on a spectrum and assume change happens over time – it is “not an instantaneous about-face.” We think it is important to note, however, that fuzzy sets don’t eliminate boundaries or definitions of sets. For example, a fuzzy set approach still acknowledges that there are mountains and plains (and clear definitions for those). The approach simply accepts that something could be in both at the same time.

Given those realities, it is not hard to imagine why fuzzy sets have not been a preferred method to use in the task of creating or defining Christian community. In such an approach, both beliefs (i.e., cognitive awareness) and practices (i.e., behaviors) do not carry much weight. In a fuzzy set, it is perfectly okay for a person to attend a Christian church service on Sunday and yet face Mecca when praying during the day. In a centered set approach, the same may be true, that is a person may attend a Christian church service on Sunday and engage in different religious practices during the week. The difference, however, is that in a centered set, the person has made a choice to follow Jesus and will change behaviors over time. That is not required in a fuzzy set. The person is allowed to mix both sets of practices in perpetuity. One can be 60% Christian and 40% Muslim, 50% Bears fan and 50% Packers fan, or 23% Canadian and 77% American. The important point is that you are not forced to choose one or the other. It is a both/and approach to categorization.

We understand why this has not been an approach favored by the Christian community over the past 40 years. It can be difficult to see how fuzzy boundaries fit with the Christian faith. Hiebert went so far as to suggest this approach can lead to syncretistic systems of beliefs and practices. Given those realities, the fuzzy set categories rarely make their way into theological, missiological, or ecclesiological conversations.

In our opinion, it seems like there might be a need for a new frame or lens through which we can view social sets. If we are following Jesus in community, it could be that we need a new way to envision that community, a new way to know who is with us. It could also be that a “new” way isn’t new at all.

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