I have been discussing the fascinating article by Keith Hopkins, “Christian Number and Its Implications,” about how many people converted to Christianity at certain points of time (say, from ten years after Jesus’ death to the time the emperor Constantine converted in the year 312).  As we have seen so far, the first problem Hopkins deals with is how to count – that is, who counts as a Christian?  Hopkins takes the (in my opinion) justifiable and sensible view that if someone considered themselves to be a follower of Jesus (whether they were proto-orthodox, or Sethian, or Marcionite, or Ebionite, or anything else) they should be counted.

The second problem, as we have also seen, is that our sources don’t give us any reliable statistics, or indeed statistics of any kind.  Instead, our sources (and, by the way, without sources we have no evidence, only guess work, even if it is educated guess work) are highly prone to exaggeration.  And so the book of Acts indicates that within a couple of months, some 8000 Jews in Jerusalem had converted.  As I’ve pointed out already, that can’t be right.

And so what do we do?  At this point Hopkins refers to the interesting study of Rodney Stark, in his book The Rise of Christianity.   Let me stress that Stark is not trained as a historian of early Christianity.  He is a sociologist who studies modern religious movements, such as Mormonism.   But as a sociologist he is very good at crunching numbers.  And in his book he crunches the numbers, coming up with some very intriguing and somewhat mind-boggling results.

Let me say before going any farther that Stark’s book was highly controversial.  He tried to establish how quickly Christianity grew.  That was the most compelling part, as I’ll be pointing out in a moment.  But most of his book was about why Christianity grew, and here he came up with some ideas and theories that simply have not seemed overly persuasive to most historians in the period, in no small measure because he did not have a very sophisticated approach to the surviving sources of the period, unlike his sophisticated approach to number-crunching.

So let me talk about the number crunching, since this also is the issue that Hopkins too wants to focus on.   Stark points out that most historians who have tried to explain the growth of Christianity have taken rather wild guesses about how to make sense of it.

Here are the data: Christianity started out as a small group of Jesus’ followers after his death – his disciples and a handful of women who came to believe he had been raised.  That much seems pretty certain and is what is reported in the New Testament itself.  There seems no reason to question or deny it.   Moreover, there is widespread agreement that even though we can’t know the exact numbers, or anywhere near the exact numbers, it appears that by the time the emperor Constantine converted, maybe 10% of the empire (or 5% or 15% — let’s just say 10%) was Christian.  It is almost always thought that the empire comprised 60 million people (give or take 10 million) at the time.   So while admitting that we’re talking ballpark numbers here, let’s assume that there were, say, 6,000,000 Christians at the beginning of the fourth century.

So the question is, how do we go from a handful of Christians at the beginning of the period we are interested in to 6,000,000 at the end?

Most scholars have preferred one of two options.  Either the growth was completely miraculous and requires the intervention of God or (or rather and/or) there had to be massive conversions of the sort you would get at a Billy Graham crusade, where at any one moment a Christian evangelist managed to convert hundreds of people to the faith at one time.  That just makes sense to most people who try to figure it out.  There must have been massive conversions to explain it, right?

Wrong.   Stark is a number cruncher.  And he studies modern religious movements, where you can actually count the converts (roughly).  And he points out that in fact it is not a matter of speculating about massive conversions.  It is about math.

For his math problem, Stark points out that the book of Acts has thousands of people converting right away in the first few months.  OK, that’s probably an exaggeration.  So let’s just say that by the year 40 CE – ten years after Jesus’ death – there were 1000 people who considered themselves Christian.   And let’s say that by the year 300 (again, we’re just doing guestimates and round numbers here for the sake of illustration) there were indeed 6,000,000.   How do we get from 1000 to 6,000,000?

All we have to do is set up an equation and figure it out.  We can safely assume that the rate of growth won’t be steady and invariable.  The rate will fluctuate over time.  We’ll admit that.  But we’ll also acknowledge that the more Christians there are, the more other people they’ll be able to convert.   If five Christians are able to convert five other others, then five hundred Christians will surely be able to convert a lot more than just five others – say, they’d convert roughly the same number, they’d convert 500, in *roughly* the same amount of time.  So if there is *roughly* the same approximate rate of conversion over time  the more Christians there are, the more converts they would be making.

And so you simply need to figure out what kind of rate of growth is needed (it will go up and down, but you only need an average).  Stark crunches the numbers.  If you start with 1000 Christians in the year 40 and end up with 6,000,000 Christians in the year 300, you need a rate of growth of (only) (about) 40% a decade.   That is to say, the 1000 in the year need to grow only by 40 by the year 50, so that then there are 1400 Christians.  By the year 60, with the addition of another 40% more; by the year 70 another 40% — keep doing the math: by the year 100 there need to be only 7400 Christians; by year 200 then there will be 210,000; and by the year 300 there will be 6,000,000.

It’s not a matter of miracle necessarily.  And you don’t need massive conversions at any point.   Assuming a steady rate of grown, where every ten years each ten Christians manage to convert, between them, only four more people to the faith, then you get to 6,000,000.   Stark is a bit more precise.  He concludes that you need a rate of grown of 43% per decade.

And for him, as a sociologist of modern religion, this is not at all implausible.  On the contrary, it’s both believable and highly interesting.   As it turns out, it is the rate of growth of the Mormon church from the time of its founding until today.

It is not a matter of miracles; it’s a matter of steady growth, and it can be accounted for by an exponential curve over time.

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