In a recent comment on my post on evangelical attitudes to homosexuality, Tony Carr claimed that: "Throughout history, the "appeasement" churches have declined, and the "fundamental" churches have grown." Putting that in a slightly less prejudicial way, it's frequently stated that in the modern West theologically conservative churches grow and theologically liberal ones decline and that statistics on changing congregation sizes backs this up. These statistics are often used either to attack theological liberalism in Anglicanism or to gloat/worry over the disappearance of liberal denominations. However, the definitional and statistical issues involved in this argument are particularly tricky, so I want to try and unpick some of them (and also draw on a very interesting website I found by a Christian mathematician).

One immediate problem is in defining theologically conservative and theologically liberal churches, especially because churches and denominations are often not internally homogeneous. This is particularly the case in the Church of England, which has a large theological spectrum with several different dimensions (e.g. Protestant versus Catholic practices as well as conservative versus liberal theology). For this reason, it's entirely possible for what looks like growth and decline in individual congregations to be largely a result of internal sorting.

For example, suppose in town X there are 5 Anglican churches, each initially with a congregation of 100. Suppose also that in each congregation there are 40 conservative members and 60 liberals, making an overall total of 500 Anglicans, 200 of whom are conservatives and 300 liberals. Suppose further that one of the churches (St Stephen's) now gets a new more conservative/fundamental minister who preaches exactly the old-time religion that all the conservative Anglicans like, but that repels the liberals within the town, and that members of the congregations then change churches to reflect this.

The end result would then be that St Stephen's, as a "pure" conservative church, now has a congregation of 200: its 40 original conservatives, plus 40 from each of the other 4 churches. Meanwhile, the remaining 4 liberal churches now have 75 members each: their 60 original liberals, plus 15 refugees from St Stephen's (assuming that those liberals leaving there move evenly to the four other churches). Therefore, St Stephen's has grown by 100% and the other churches have declined by 25% without a single person changing either their denomination or their theology. In fact, St Stephen's might show considerable growth even if they actually drive some people away from Christianity altogether. Suppose only 40 of the original liberals in the congregation move to other churches and 20 leave the church altogether. St Stephen's still grows to 200 and the other churches congregations fall even further (to 70 members each), even though it is St Stephen's that is the reason for these Anglicans leaving.

Of course, it would be equally possible for the statistics to go the other way round. If just one of the church in the town had a minister or policies that particularly appealed to liberals in other congregations (they are gay-friendly or have a particular enthusiasm for interfaith dialogue etc) then they may similarly grow at the expense of other churches. But I've put it this way round because it tends particularly to be theological conservatives who encourage the leaving of one congregation for a "purer" one. The example I've given also shows another important point: growth figures for relatively small churches can look very impressive without actually referring to many people.

If you're looking at figures for growth or decline of denominations, therefore, it makes sense to focus on ones which are large, relatively homogenous within themselves and which are quite dissimilar from other denominations (so that you're not just seeing people move between very similar churches). And once you do that the claim that conservative denominations are growing looks a lot shakier. For example, the Catholic Church has serious problems in the US and in Europe (its numbers are holding up or growing in the US only because of Catholic immigrants and are in slow decline in Britain). The largest Protestant denomination in the US, the Southern Baptist Convention is declining and so are some other evangelical denominations. This isn't to deny that liberal denominations are also in trouble (and in some cases their numbers are declining much more steeply), but they do show that theological conservatism alone is not the answer.

Which brings me to a very interesting website: Church Growth Modelling run by John Hayward of the University of Glamorgan. Hayward has developed several models of church growth, essentially adapted from epidemiology. Christianity here is something that non-believers "catch" from enthusiastic church members, but such enthusiasts do not keep on making new recruits. Their evangelical "infectiousness" declines and they became inactive as recruiters, even while continuing in the church. Hayward builds up several possible layers of the model, as shown in this diagram:

renloops

Hayward's model of church renewal

He then runs simulations using different parameters to explore both the short-term and long-term effects of two key factors: the reproduction rate of individual enthusiasts (bringing others into the church who then go on to bring more new members) and also the success of the church at retaining the children of believers to become committed adult members of the church (whether active or inactive). Hayward's models are particularly interesting because they suggest that short-term expansion can sometimes be at the expense of longer-term growth and that sustained long-term growth is very difficult to maintain (although a stable higher size can be maintained for longer). Hayward's models of long-term decline are also revealing: for example he calculates that on present trends the Church of England will be down to around 80,000 members by around 2100.

Hayward's models aren't the only possible way of looking at church growth (and he admits himself that there are some unquantifiable factors that he can't model), but they are very useful for thinking about how churches behave. They're also potentially useful for looking at other religious organisations; I immediately wondered whether a similar model would also explain the rapid growth and then decline/stabilization of new monastic orders in the Middle Ages.

Another paper by Hayward also provides an interesting definition of a strict church (p. 3): "A strict church is one that has a strict entry policy, a policy that prevents a number of people from joining the church who would have otherwise wished to join. Conformity is expressed through the recruitment policy. Thus a strict church will be pure in the sense that people are filtered out by some set criteria."

Hayward's criterion is interesting precisely because it reminds us that a strict church isn't necessarily a conservative one: a church that didn't care what you believed about Biblical inerrancy or evolution as long as you were willing to sell all your goods and give the money to the poor is an extremely strict one. But it does also apply reasonably well to many theologically conservative denominations and churches: if you have to sign up (literally or figuratively) to a detailed doctrinal statement or commit to attending several services a week or to avoid drinking alcohol, that is a deterrent to the less zealous. He goes on to show that under some certain assumptions about how strictness affects the enthusiasm of new members who are accepted, a strict policy may in the long-run be more effective than a more lenient one of letting everyone who wants to join a church do so. (Although a too-strict church may also die out, like the Shakers).

So why don't all churches do more evangelism and hence bring more people in? Is it just lack of belief or liberal wishy-washiness that prevents this? Here, I think there's one arrow missing from Hayward's renewal model (depicted above). Hayward pictures enthusiasts as having either a positive or neutral effect on unbelievers. I think he needs an extra arrow to explore the possibility of negative evangelism. Hayward allows for adults already in the church to leave it and become actively disillusioned with it (his "active reversion"). Such "hardened unbelievers" are temporarily resistant to all conversion attempts. But it's also possible to become hostile to a church/religion that you're not part of as a result of unpleasant contacts with its enthusiasts. Unbelievers can be turned to hardened unbelievers without going "through" the church first.

Such negative evangelism can take many forms. At its extreme, major events like the Catholic church's handling of child abuse scandals or the militancy of some Islamic sects can turn potential converts off entire denominations or the thought of any kind of religion. At the other end, door to door missionaries or just an unpleasant encounter in a church playgroup may make people reluctant to engage with Christians again. I'm not sure how you could quantify the effects of such negative evangelism, but they certainly do exist. I suspect that many people in more liberal churches have experienced such negative evangelism themselves and are therefore wary about too explicitly missionary an outreach.

The other point to make is that Hayward's model, because it's adapted from epidemiology, is a supply-side model; if there's enough of a supply of Christianity, some people will "catch" it. He doesn't model the demand for religion and particular types of religion. There's an interesting assumption shared by both the more conservative Christians and the more 'missionary' atheists, that there is only one real form of Christianity and that is fundamentalism. Any other kind is lukewarm, wishy-washy stuff that appeals to no-one. So if you don't believe literally in the Bible you can't really be a Christian and you're inevitably going to end up as an atheist.

That black and white assumption, however, goes against the whole grain of modern life. People don't just want to have two choices on anything; and as the metaphor of the religious marketplace suggests, religions and denominations are increasingly competing against one another. The evidence that there is no demand for liberal Christianity seems to me very weak. It may only be a niche product, but some people are still going to want it.

And it's possible to see where that niche might fit roughly into Hayward's renewal model. He assumes that the active and inactive believers (in terms of recruitment) are both within the same church or denomination. But the same model would also work if we presume that enthusiasts whose enthusiasm fades or inactive believers who are renewed move between two different type of churches: strict evangelical ones (call them alpha churches) and more lenient and less mission-focused churches (call them beta churches). If moving denominations or churches becomes standard practice (and it's already very common in the US), you are likely to see more of this happen.

I've discussed this idea before, in terms of hard and soft churches, and as commentators then pointed out, there is earlier work on the topic. What's new in Hayward's work is the attempts at quantification, and if I had more time and energy it would be interesting to combine Hayward's model with data on switches between denominations. I suspect this might show that some denominations (such as the US Episcopal Church might survive for longer than expected via influxes of disillusioned Catholics.

I'm less certain about what the future holds for liberal denominations within the UK: it would be perfectly possible for liberal Christianity as whole to survive while some individual denominations effectively disappeared. To an outsider like me, it's not clear whether there's enough distinctiveness between say, URC churches and Methodist ones to keep them both going. The niche for a lenient congregational-based church with a low-church style of worship looks overcrowded at the moment, and there are also new contenders for such markets, such as the Emerging church movement. But if strict churches are going to stay strict, they need the lenient beta churches to absorb the non-zealous or no-longer zealous. Despite the hostility of traditionalists towards liberals (and vice versa) there is real symbiosis between them and we ought to think realistically about that.