Stark, Rodney. "Chapter 1: Conversion and Christian Growth." The Rise of Christianity: How the Obscure, Marginal Jesus Movement Became the Dominant Religious Force in the Western World in a Few Centuries. San Francisco: Harper Collins, 1997, 3-28.
Stark, recognizing the phenomenal growth of Christianity in the early centuries, sets out to articulate one central question, "How was it done?" (Stark 1997, 3). From a sociological point of view he analyzes the way conversion growth would need to have taken place in the first few centuries. There were certainly doctrinal reasons, but there may have been very important additional factors in play as well (Stark 1997, 4).
The biblical record in Acts 1:14-15, Acts 4:4, and Acts 21:20 describe growth from about 120 to several thousand in Jerusalem over the course of less than 30 years (Stark 1997, 5). Stark does observe that "Origen admitted that Christians made up 'just a few' of the population. Yet only six decades later, Christians were so numerous that Constantine found it expedient to embrace the church" (Stark 1997, 5). From a sociological standpoint, then, Stark asks how such a growth would take place. By Constantine's tie, there are estimates of 3 million (a low, by Gibbon) and 15 million (a high, by von Hertling). Stark considers the likely range to be more like 5-7.5 million (Stark 1997, 6). This would represent a growth rate of about 40 percent per decade. A rate of 30% would yield a result under a million, while a rate of 50% would result in nearly 38 million. Stark concludes that a fairly steady rate of conversion and biological growth is sufficient to explain the outcome.
Stark does note that this model suggests progress which would seem very slow. By the year 100 there may have been only about 7500 Christians. This corresponds to estimates by Robert Wilken and L. Michael White. By the year 250 Christianity may have reached almost 2 percent of the population (Stark 1997, 8). Yet, if growth remained proportional, Christianity would have remained on the trajectory toward dominance by the early fourth century.
There is some evidence that the church in Rome was larger, proportionally, than in some other areas. Eusebius quotes correspondence from Dionysius of Corinth indicating that the Christians in Rome were known for generosity. Yet it may well have remained a relatively small proportion of the population (Stark 1997, 9).
Stark further explains the conversion of Constantine as more likely a result of the growth of Christianity than a cause. Likewise, the relative lack of success of the Diocletian persecution in 303 can be explained by the growing acceptance of Christianity. By this time, following Stark's pattern of growth, nearly half the empire may have been Christian (Stark 1997, 10).
Stark notes what may be independent corroboration of the growh pattern. In the 1980s Roger Bagnall tracked growth of Christianity in Egypt by identifying distinctively Christian names. He found a similar pattern of growth between 239 and 315 (Stark 1997, 12).
At some point, the curve would flatten, probably near the end of the fourth cnetury, because the overall culture would become saturated (Stark 1997, 13).
Stark considers the nature of conversion growth. Though there are accounts of conversions of large groups, these events are not entirely necessary for the spread of Christianity (Stark 1997, 14). Stark's earlier research on religious conversion, in the early 1960s, involved observing growth of the Unification Church in San Francisco (Stark 1997, 16). The people who converted had strong ties with people who were already associated with the group. The ideology was normally secondary to the relationship (Stark 1997, 17). In essence, Stark sees conversion as an act of deviant behavior, which re-orients one into a community where the behavior is the norm, rather than the exception. Conversion growth is normally built on a foundation of personal relationships (Stark 1997, 18). Of note is a conclusion Stark makes about religious movements. "Most new religious movements fail because they quickly become closed, or semiclosed networks. That is, they fail to keep forming and sustaining attachments to outsiders and thereby lose the capacity to grow" (Stark 1997, 20). It is clear to Stark that the early Christians maintained open networks, which allowed for their rapid and sustained growth. Stark gives on to consider whether this is a concept which can be generalized across cultural lines.
Stark notes that the potential participants in networks change based on time and culture, and that the size and strength of the networks may differ, but that the concept is stable over time (Stark 1997, 22).
In fact, lacking comprehensive information about specific situations, we are forced to reconstruct some information, hoping to approximate reality. Stark is uneasy with this practice, since it has been used to apply inadequate models to cultures (Stark 1997, 23). As an example, he cites the difficulty inherent in the use of the word charisma, which means something quite different in modernity than in antiquity. Definition of terms is very important, as is lear definition of overarching concepts (Stark 1997, 24-25). Stark considers that an adequate reconstruction can only be done with the best social science theories put to use to explain, interpret, and harmonize what we know, thus enabling us to come to good conclusions about what we do not know (Stark 1997, 26).