The "Emerging/Emergent Church" movement, by its own intention, is impossible to define or even describe properly.
However, what seems in common is that all such Emergents believe the church must engage in the missio dei (that is Latin for "Mission of God").
It is argued that God is working. The responsibility and task of the church is do what God is doing.
The understanding that the church should be active in doing the mission of God makes us ask questions about whether our churches are doing enough. This is not a new question. Many of us, long before the Emerging Church, have asked this question because we have felt the stagnation that often besets churches.
Members or partners?
During the boom of the Church Growth movement in the 1980s we were called to move our churches from being "modalities" to become "sodalities". A modality is a collection of people that exist as a mode of being. You belong by just being. Families are modalities. A nation is a modality. Membership requires no or very little commitment, you are part of it just by existing.
Modalities are about "being".
Sodalities are like partnerships. You have to apply and work hard to join. You join to engage in a task that must be done, and it requires a high level of commitment. Sodalities are about "doing".
There are huge advantages in being a sodality. Stagnation is overcome. Everyone is involved. All members are working and pulling in the same direction to reach a goal.
The problem in making church a sodality is that the Bible describes church as much more like a modality. The images of church are that of family, where relationships are significant. What matters most for us, as an individual in a church, is that the belong to Christ in a relationship forged by his substitutionary death for us, not what I contribute to the outcome.
I don't want to say the existence of churches doesn't achieve anything. Things are achieved by the good functioning of the church family.
As an example take the Chappell family. All three brothers played cricket for Australia. As children they played cricket in the back yard, which is what families do. I am certain their functioning in this way as a family also made them better cricketers. I am also sure part of their success was the athletic DNA they inherited. The modality of their family resulted in them being outstanding sportsman. But they weren't family in order to become great sportsmen.
The challenge facing us in church is not to do more, or to do it better, but to shape our being a church family together in such a way that we all become white hot in our love and service of Jesus.