Looking at this subject I thought about a word that in many Bible translations is translated as 'maturity', but in other translations is translated as 'perfection'. The Greek word in question is Τēλιος. Its basic meaning is 'the purpose for which a thing was designed'.

If a watch is τελιος it keeps perfect time; if a human being is τελιος, he, or she, is holy. But what does it mean for a church to be τελιος?

What is maturity?

What is the purpose for which the church was designed?

When is a fresh expression of church τελιος?

The purpose of fresh expressions is to reach people who are beyond the reach of inherited church. The reasoning is that we are in a missionary type of situation. So if we view the UK as a mission field and fresh expressions of church as the mission movement, how do we judge maturity?

Rufus Anderson and Henry Venn came up with the idea of the 'three selfs': self-government; self-support and self-propagation. A fourth self was added by David Bosch: self-theologising.

By that standard, a fresh expression of church is mature when it runs itself. It is self-governing. That doesn't mean when it has a fully functioning PCC or church council, complete with wardens or stewards or whatever. It's hard enough for inherited churches to find people to fill those positions. What it means is that there is a committee of sorts that is running the church and it has been recognised by the sending church as being grown up enough to make its own decisions – even if it makes a few wrong choices. The formerly unchurched are now running the fresh expression.

Self-supporting means that financially it can stand on its own feet. This doesn't lead to independence. It leads from dependence, through independence, to interdependence.

But it is mature when it is paying its own rent; providing its own resources, but maybe still receiving gifts from its parent(s).

And self-propagating! Have we got that far yet? Do we have fresh expressions of church starting even fresher expressions of church? 'The life cycle of all living things includes the creation of the next generation' (George Lings). Of course reproduction doesn't happen until a certain level of maturity has been achieved.

Then there is David Bosch's extra: self-theologising. We don't create our own doctrines, but we do need to become contextual theologians – interpreting what God is doing in our context and applying ourselves to that.

Steven Croft, in the early days, talked about going from 'fresh' to 'stale' expressions. I have come up with an alternative. In East Sussex there is a little village with its own Anglican church. The village is called Ripe and the church is called 'Ripe Church'.

I like to think in terms of τελιος. What does it mean for a fresh expression of church to fulfil its purpose?

Does it mean settling down to conformity?

When we have enough people to call ourselves 'proper' church is that when we are mature?

Or are we mature when we have achieved the three selfs? We can sustain ourselves, but we are still maintaining our purpose of reaching people who are beyond the reach of inherited church.

I think there is no one answer to what maturity looks like, but I don't think it is achieved by giving up the purpose for which the fresh expression was intended.

Maturity in fresh expressions of church means that we are doing what we set out to do and we are doing it better. In the process we have become self-governing, self-supporting, self-theologising and, hopefully, self-propagating.

Martin is minister of The Haven Church, Eastbourne. Haven, which he helped to plant in 2002 for unchurched young adults, meets at The Haven School in the town's Sovereign Harbour. It is a Methodist/Church of England Local Ecumenical Partnership.

Sorry Paul, but that's not missional! It may well be important and necessary work, but it's not missional. But I do think Paul highlights an important discussion concerning what we mean by 'missional'. The danger I find is that with many emerging churches, everything is missional but mention evangelism at your peril.

Yet David Bosch, whose work on the Missio Dei is at the heart of our missional language, writes: 'Evangelism is the core, heart or centre of mission. We do not believe that the central dimension of evangelism, as calling people to faith and new life can ever be relinquished. I have called evangelism the heart of mission. With evangelism cut out, mission dies: it ceases to be mission' (Evangelism: Theological Currents and Cross-Currents Today).

Now, I am not suggesting that evangelism and mission are synonymous, but I do believe that evangelism is at the very heart of mission. We do not help the fresh expression movement if we are not enabling unchurched people to become transformed and transforming disciples of Jesus. As I have written elsewhere, we have too many safety nets and not enough fishing nets.

We also do evangelism a disservice when we divorce it from discipleship. As Graham Cray says in the June edition of the e-xpressions newsletter, we need both quantity and quality. It is about winning people to Christ, but it is also about the qualities of discipleship that we are seeing developed in new converts and their communities.

The danger is we reject evangelism because our present (or past) models are deficient for this age. But that's no reason to excuse ourselves from the work of evangelism. The need is great today and so we must to do the hard work of seeking out and developing good, faithful and relevant models of evangelism. (There is no one model!)

Scott McKnight, the American theologian, in a recent article in Christianity Magazine (April 2009) on the emerging church, put it most bluntly and starkly when he wrote, 'Any movement that is not evangelistic is failing the Lord.'

Dave Male is involved in training pioneers in two Anglican theological colleges in Cambridge and is planting a church to connect with sports people, called Relay. His blog is here.

If you have something burning to say and want to contribute to the Share weekly guest blog, please contact Beth Keith.