The Family Tree and Wave Models

It is "National Siblings Day" in the US as I write these words. While this day is hardly a significant date in the church calendar, it does bring to mind the concept of "sister churches." This phrase tries to convey a sense of equality, both of current status and of historical roots. As such, it is generally a positive assessment when one church considers another to be a "sister church".

The term "sister church" evokes the idea of a family tree, thus allowing us to talk about "daughter churches" which split off from "mother churches", and by extension "grandmother" and "granddaughter" churches. The family tree metaphor should not be pushed too far -- for example, what church is at the root of the tree, thus representing the initial church of Acts: Catholicism or Orthodoxy? That question is essentially one of polemics between the various branches of Christianity, rather than one which can be easily and objectively answered.

The family tree model finds its origin in genealogy, but has been used in other fields as well, where two or more current entities share some sort of common origin. In biology, the family tree model is the root metaphor for taxonomy. In historical linguistics, the family tree model is the traditional representation of relationships among members of a language family.

In this latter case, there is an alternative to the family tree model, known as the wave model, in which changes to a language move out from a given dialect to its neighbors. Could such a model be useful in ecumenical relationships? It may be useful in describing the interrelationships among various Protestant bodies after their separation, as theological influences do not respect denominational lines. (Indeed, the influences also affect Anglicans, Catholics, and Orthodox, but these latter groups tend to be more self-defined and thus have stronger senses of identity.) I do not know of any attempts to systematically organize Protestant bodies in a wave model format in detail, though the groupings such as "mainline", "evangelical", "charismatic", "fundamentalist", and the like are attempts to do so in general, as churches can split off from a parent body in one group to take on the characteristics of another group. In some sense, then, the organization of Christian bodies might be best done by a combination of family tree and wave models.

The ecumenical payoff of this argument is the following. Churches most easily negotiate a union (or reunion) when there are relatively few differences between them. The family tree model can suggest churches which are similar, but the results, especially among Protestants, needs to be checked by the wave model. Realistically, this analysis is only for ecumenical theorists to explain why two or more churches are compatible; the churches themselves are unlikely to use this analysis to find a union partner. Rather, churches will be attracted to each other based on closeness which results from the effects of the family tree and wave model relationships.

In short, the family tree and wave models are theoretical tools which ecumenists can use to describe the relationships between churches. Such models can be used to explain why certain mergers, or even coalitions on issues, form. They cannot determine mergers: both models are fairly insensitive to both the nature and the significance of differences between two churches. In theory, two churches might disagree on only one issue. This combined family tree-wave analysis would suggest that these two churches could merge easily. If the difference is on some other issue which one or both churches considers essential to the Christian faith, and neither is willing to change its position, then a merger is not easily but impossible.