I have come to think of the Holy Spirit as being sort of a zero. That may sound heretical but stick with me for a couple of paragraphs before you bring out the torches and pitchforks.
Consider the role of the number zero in our mathematical system for a moment. Zero has no value. It represents nothingness; the absence of anything. As a result, it could be tempting to think that zero is unimportant. But it also serves as a place holder in our number system, reminding us that there is value represented by this number that has no value. What's the difference between 1 and 1,000,000? Nothing but a bunch of zeroes.... and 999,999 The reality is that without zero serving as a placeholder, our entire number system would fall apart. It would be meaningless. We would be unable to distinguish 1 from 1,000,000. Lacking the number zero wouldn't change the reality that there is a difference between 1 and 1,000,000. It would simply inhibit our ability to express that reality and therefore would limit our ability to carry out more complex mathematical computations. The number that means nothing makes all the difference.
It seems like the Holy Spirit sort of functions the same way in our theology. I believe that the Holy Spirit is active in my preaching, in the reading of Scripture, in the life of our community of faith forming us into the likeness of Christ. I believe that without the Spirit all of these things, even Church itself, would be meaningless. Yet have you ever tried to put your finger on the activity of the Spirit? When I preach, can we separate what was me and what was the work of the Spirit? When we interpret Scripture, which part of our interpretation is good scholarly research and which is the Spirit speaking? And when our church looks more like Christ, is that the Spirit moving or merely people being good people? The reality is that while we believe the Spirit is active and cooperates with our spirit in these things it also impossible to quantify the work of the Spirit of God... and for us it seems the temptation is always to think that saying something can't be quantified is the same as saying it has no value. Since we can't say exactly what the Spirit is doing its not long before we begin to think or at least act as if the Spirit's not really doing anything and that this Church stuff is entirely up to us.
But to speak of being the Church without the work of the Spirit is like saying 1 = 1,000,000. The difference between the Church in the power of the Spirit and whatever we call a random assembly of people singing a bunch of worship songs may appear to be nothing, a series of nothings, a series of unquantifiable happenings that appear to have no value. But that series of nothings means everything. It completely changes the equation. It brings exponential transformation while remaining virtually unnoticed itself.
Often as I listen to people verbalize their faith, I hear a lot of talk about God the Father and Jesus. The Holy Spirit seems to be the poor, forgotten step child of the Trinity, at least in the ways we often articulate our faith. Of course, lacking the Holy Spirit in our theology doesn't change the reality that the Spirit is at work in the Church. It simply inhibits our ability to express that reality and therefore limits our ability to more maturely understand who it is that God wants us to be. Without recognizing the work of the Holy Spirit, all kinds of heresies arise in our theological formulations. We begin to think that Jesus is merely an example to be imitated and that we can do that on our own so we don't understand why others don't just pull themselves up by their bootstraps like we did and become more Christ-like and as a result we become very un-Christ-like in our attempts to imitate Christ. Or we think that God's work is primarily about forgiving us through Jesus' death so all we have to do is accept that forgiveness and there is no further work of transformation to be done in our lives so its ok that we aren't like Jesus because we could never be that perfect anyway. Or we think evangelism and church growth is up to us and our programs...or on and on. Good theology doesn't guarantee good practice but it at least helps us know the kind of practices to which God is calling us. We not only need the Holy Spirit to be the Church. We also need the Holy Spirit to be prominent in our articulations about the Church. Without serious and deep reflection on the work of the Holy Spirit among us, our spiritual maturity will resemble the math skills of a child who can't count past 9.