Throughout the history of the Christian church, Christianity has been constantly shaped and reshaped with various groups and sub-groups. Fairly early in Christian history, Catholicism divided into eastern and western groups—Orthodox and Roman (Eastern and Western). In the Reformation, (Roman) Catholicism was opposed by Christian reformers. The nationalism of the European Reformation was one motivation for the search for religious freedom which led pilgrims and others to the shores of North America.
That we may be on the cusp of yet another restructuring of basic Christian groupings is clearly possible, but the exact nature of the alliances and which groups will recognize which other groups is not yet clear. What is clear is that the previous ways of thinking about Christianity and Christian groups appears to be going away. The well-defined doctrinal distinctions which provided identity and distinctiveness are giving way to new commitments based on practices and methods.
In the middle of the last century, a tract popular among churches of Christ summarized the religious options as Protestant, Catholic, Jew, and “us”. While that paradigm was, at the time, an interesting approach that caught the attention of many and uniquely positioned us outside the typical religious understandings (now hardly more than an intriguing part of history), the division is hardly valid today as we have seen the multiplication (or explosion) of Christian groups that are neither Protestant, Catholic, nor Jew. The paradigm is much less helpful in defining or distinguishing Christian groups at the beginning of the 21st century.
Today, one might mention at least the following groups within Christianity: denominationalists, Pentecostals, Restorationists, community churches, independent faith communities, and sects and cults. Based on method, one might mention the house church movement (include or add SIMPLE churches, cell churches, etc.) which develops groups that accept or recognize one another based on methodology. The same thing could be observed, but to a lesser extent, in the church planting movement (CPM) and Emergent church movement.
[More on this topic tomorrow. Also see my article: Christian Groups and Evangelism.]