ACADEMICS can be irritating, and not only when they are protecting their railings with signs written in Greek and Latin, as was seen in Cambridge last week. It is hard to get a straight answer out of them. When Professor David Voas, Laura Watt, and a team from the University of Essex reported their findings on the causes of church growth, they hedged the results about with caveats and provisos. When the findings were translated into a book for general church use, From Anecdote to Evidence, a number of these caveats fell out. More disappeared when the book was converted into a website, From Evidence to Action. Church leaders can be heard regularly saying, "We now know what causes growth." An examination of the evidence by the Revd Dr Mark Hart, a rector in the diocese of Chester, From Delusion to Reality, published this week, suggests otherwise.

The trouble about church growth is not that nobody knows how to generate it but that everybody does. Each churchgoer knows what he or she likes, and is convinced that just a little more of it will bring in more people. And so it might. There are many churches that have attracted all the available people in the locale who like choral music, or long, confident preaching, or a good Sunday school at the right time of day, or whatever "it" is. But there are plenty of other "its" that might attract different sorts of people - and anyway, as the Fresh Expressions movement struggles to maintain, there is more to evangelism than attracting people to services.

It would be wrong to belittle people's instincts and experience. It is, after all, easy to recognise what puts people off church. But to have the "evidence" of what attracts them codified into a series of eight "factors" - clear mission and purpose; actively engaging with local context; willingness to change and adapt; a welcoming culture, ongoing relations; leaders innovating, envisioning and motivating; lay people active in leadership; engaging children and young adults; nurturing disciples - needs to be much more tentative, especially if these are going to be benchmarks for whether a church receives any of the Church Commissioners' proposed new funds. To take just one example, the headline idea that groups of churches fare less well than a single-building parish: Dr Hart suggests that weaker churches tend to get put into groups; stronger churches stand alone. Or there is the notion that ambitious, visionary clergy are drawn to churches that already have the building-blocks for growth. These are thus factors associated with growth, but not necessarily causes.

The difficulty is that God confounds all the easy answers. It makes sense to have services that are clear and easy to understand; but God is neither. To provide a warm, friendly welcome; but God often calls people apart to address them. To communicate the good news; but God can choose to remain silent. There is no reason to stop doing the obvious, natural things; but it is important to keep St Paul's warnings in mind: the Church can prepare the soil and plant the seed, but the God who provides the growth is a lover of biodiversity.