The Explosion of Early Christianity, Explained

Originally posted at Common Sense Atheism: Luke Muehlhauser gives an explanation for the explosion of Christianity in its’ early years.  It is, I think you’ll find, a rather natural one.

In just 300 years, Christianity grew from a small Jewish sect in Galilee to become the dominant religion of the Roman Empire. How can we explain this?

A popular explanation is mass conversion. Acts 2:41 reports that Peter converted 3,000 people with a single sermon. Early church historian Eusebius wrote that the apostles “went on to other countries and nations with the grace and cooperation of God, for a great many wonderful works were done through them, by the power of the divine Spirit, so that at first hearing, whole multitudes of men eagerly embraced the religion of the Creator of the universe.”1

Modern thinkers tended to agree. Yale historian Ramsey MacMullen wrote that Christianity grew so quickly that it must have had “successes en masse.”2

Christians explain these mass conversions with supernatural miracles; proof that Christianity is true! Even atheists think the early Christians must have been such good preachers they converted whole audiences. Whatever the explanation for mass conversions, it seems that Christianity could not have grown so fast without them.

At least, that’s what we thought until 1996, when somebody actually bothered to do the math. That man was Rodney Stark, sociologist of religion.


The math is pretty simple. Let’s do it ourselves. We need two numbers: a early starting count of Christians and a count around 300 C.E. Here’s Rodney Stark writing about the starting number:

For a starting number, Acts 1:14-15 suggests that several months after the Crucifixion there were 120 Christians. Later, in Acts 4:4, a total of 5,000 believers is claimed. And, according to Acts 21:20, by the sixth decade of the first century there were “many thousands of Jews” in Jerusalem who now believed. These are not statistics. Had there been that many converts in Jerusalem, it would have been the first Christian city, since there probably were no more than twenty thousand inhabitants at this time… As Hans Conzelmann noted, these numbers are only “meant to render impressive the marvel that here the Lord himself is at work” [1973:63]. Indeed, as Robert M. Grant pointed out, “one must always remember that figures in antiquity… were part of rhetorical exercises” [1977:7-8] and were not really meant to be taken literally. Nor is this limited to antiquity. In 1984 a Toronto magazine claimed that there were 10,000 Hare Krishna members in that city. But when [researchers] checked on the matter, they found that the correct total was 80.3

So let’s say there were only 1,000 Christians by the year 40, a full decade after Jesus’ death.

As for the ending number, at 300 C.E., historians have made many estimates, usually around 5-8 million.4

So, Christianity may have grown from about 1,000 believers in 40 C.E. to about 5-8 million in 300 C.E. – just 260 years. That would require a growth rate of 40% per decade, as shown by this table:

Year Number of Christians, given 40% growth per decade
40 1,000
50 1,400
60 1,960
70 2,744
80 3,842
90 5,378
100 7,530
150 40,496
200 217,795
250 1,171,356
300 6,299,832
350 33,882,008

That really is tremendous growth. Now we can ask, does this kind of growth require mass conversions?

As it turns out, this matches almost exactly the growth rate of the Mormon church over the past century. Mormonism has grown at 43% per decade, and without mass conversions.5

Exponential growth explains the explosion of Christianity perfectly. In fact, it also explains why Christianity seemed insignificant until about 300, when it suddenly became a huge force in the Roman Empire.6 The growth rate remained the same, but in terms of absolute numbers, Christianity would indeed explode around that time – from 6 million to 33 million adherents – if it tracked with the growth rate of Mormonism.

So, the early growth of the Christian church is impressive, but no more impressive than the growth of Mormonism.

And in fact, Christianity had several advantages that Mormonism never had.

For example, Christianity was the only missionary religion in the Roman Empire. Jews and pagans did not try to convert each other. Christianity had that field all to itself. Contrast that with the world faced by Mormonism, in which dozens of missionary religions compete with Mormonism for new adherents.

Second, Christianity was an exclusivist religion. If an ancient Roman converted from one brand of paganism to another, he was free to keep his old gods. One brand of paganism gained an adherent, and another did not lose one. But Christianity was intolerant of other beliefs. If someone converted to Christianity, then Christianity gained an adherent and paganism lost one. This was also true of Judaism, but Jews did not evangelize. Mormonism is also an exclusivist religion, but it is competing mostly with other exclusivist religions (Christianity and Islam).

Third, Christianity offered equal status to women, who had very low status in Judaism and in Roman society. Instead, Mormonism actually offers women lower status than in the society at large – hardly an attractive feature to half of all potential converts to Mormonism.

Fourth, we have no mention of primary evidence relating to Jesus that ancient people could use to defend or discredit Christianity. In contrast, primary evidence that discredits the bogus career of Joseph Smith is easily available, because he lived in the modern era.

Fifth, Christianity competed only with Judaism – which had no missionaries – as a text-driven religion. Texts are a powerful way to spread, unify, and preserve religious movements, and the pagan world had few of any importance.7 In contrast, Mormonism had to compete with dozens of other text-driven religions during its infancy, most notably orthodox Christianity and Islam.

Sixth, after Emperor Constantine converted to Christianity, whole villages thought it best to “convert” to Christianity,8 and entire cities of barbarians “converted” with their leader when their settlement was subsumed in the Roman Empire.9 Mormonism has never benefited from such state support.

Even with all these disadvantages compared to early Christianity, Mormonism seems to have slightly outpaced the growth of the early Christian church.

Clearly, we have no need of mass conversions or magical explanations. The early growth of Christianity is, actually, much less impressive than the growth of Mormonism in the 20th century, which required neither mass conversions nor miracles.

The explosion of atheism

There is another problem for Christians who want to say that the explosive growth of early Christianity must be due to God. Compared to Christianity, atheism grew even faster during the 20th century. According to the World Christian Encyclopedia (the most respected source for religious demographics):

The number of nonreligionists…  throughout the 20th century has skyrocketed from 3.2 million in 1900… to 918 million in AD 2000… From a miniscule presence in 1900, a mere 0.2% of the globe, [atheism and agnosticism] are today expanding at the extraordinary rate of 8.5 million new converts each year, and are likely to reach one billion adherents soon. A large percentage of their members are the children, grandchildren or the great-great-grandchildren of persons who in their lifetimes were practicing Christians.

At the early Christian rate of 40% per decade and 3.2 million in 1900, non-believers would have only numbered 74 million in 2000, not 918 million. The growth rate of non-belief in the 20th century was 76% per decade.

The percentage-of-world-population gain for atheism was even greater. Christianity claimed about a third of world population in 1900, and claims the same today. Hindus stayed at 1/7th of the world total throughout the century. Buddhism and paganism have declined. Islam went from 1/8th to 1/5th – not through freedom or education but through unprotected sex. In contrast, non-belief during the 20th century skyrocketed from 0.2% to 15.2%! Clearly, the gods are not winning.

Of course, atheism is not a religion, so the comparison is not fair. But what are Christians supposed to make of this? Did Satan strike a big blow to Yahweh, who is now losing the battle? Did a god who likes atheists take over? Or is our planet – which became literate and educated as never before in the 20th century – finally growing up?



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