I’ve been reading a lot during this pandemic, and I just finished reading The Triumph of Christianity:  How a Forbidden Religion Swept the World by Bart Ehrman.  It’s about the rise of Christianity from Pentecost to the end of the reign of Constantine, the first Christian Roman Emperor.  It’s a serious history book, but it’s written in a style that makes the subject accessible to a general readership.  I’d like to talk about how quickly the Gospel spread during those early years.

            Ehrman gives estimates of the number of Christians at different dates, given in the table below, which are based on earlier calculations by Rodney Stark.  Different methods give different estimates, but they are all within an order of magnitude; I think the numbers in the table are averages of the different estimates.  The number for the year 350 AD is about half the population of the empire. 

Mathematical models for the spread of COVID-19 have been in the news a fair amount for the last two months, and as a math person I find descriptions of them very interesting.  Over the years I have seen talks describing a number of related models; some population growth models, some predator-prey models, and some spread of contagion models.   The simplest such models are for bacterial growth and are taught in first-year calculus.  They predict exponential growth (until they run out of food).  If we were to graph the data in the table, we would find that it too looks like an exponential curve; like all such curves it muddles along pretty much flat for a while, and then all of a sudden explodes.  How quickly that happens depends on the growth rate.  For the data in the table the average growth rate is a little over 3 per cent.  Stating it another way, a church of 100 people would have gained 3 people (or one family) each year.  That seems pretty modest, but it yields the huge growth of the church in the first four centuries.

            We have been commissioned to spread the Gospel, but we often get discouraged when we see only modest success.  I think we should take comfort in this numerical history of the early church.  It shows that we shouldn’t focus too much on numbers; our focus should be people, the neighbors of which Christ spoke.  It also shows that continued small short-term successes lead to huge long-term ones, and the keyword here is “continued.”  We need to have faith to continue our efforts; fortunately, we have God’s unconditional love to support us.

Jim