There's an objection that any serious Christian will raise against the whole project of studying the church's structure. Where is God in this? With all this talk of attachment, group dynamics, architecture and incentives, is formation being reduced to social engineering? Has the Holy Spirit been replaced by a floor plan?
The objection deserves a direct answer. The best one comes from Thomas Aquinas, a theologian who spent his life on exactly this question, and from his principle that grace does not destroy nature; it perfects it.
What the principle means
Aquinas's claim is that God's saving action works through the creature's nature and never bypasses it. When God makes a person holy, he keeps that person's humanity and heals it, elevates it, and brings it to what it was made to be. Grace presupposes nature, because it needs something to perfect.
That has an immediate consequence for the church. If human beings are, by nature, social creatures who form through relationship, then grace will form them through relationship as well. A theology in which the Spirit sanctifies people regardless of their environment, their bodies, their habits, and their neighbors is a theology in which grace destroys nature. Neither Aquinas nor the New Testament teaches it.
Scripture says the same thing.
Two are better than one; because they have a good reward for their labour. For if they fall, the one will lift up his fellow: but woe to him that is alone when he falleth; for he hath not another to help him up. (Ecclesiastes 4:9-10)
The wisdom of Israel treats the need for companionship as a fact about the creature. And when Paul plants churches, he plants households instead of isolated converts.
The four causes, and the one this is about
Aquinas inherits from Aristotle a fourfold analysis of why anything is as it is. The material cause is what a thing is made of. The efficient cause is what brought it about. The formal cause is what makes it the kind of thing it is, meaning its structure and its arrangement, and the final cause is what it's for.
A bronze statue is the standard illustration. Its material cause is bronze, its efficient cause is the sculptor, and its final cause is the honoring of someone. The formal cause is the shape. Bronze is also what a bell is made of, and a bell isn't a statue, and the difference isn't in the bronze.
Apply the analysis to a congregation. Its material cause is its people. Its efficient cause is the gospel and the work of the Spirit, and its final cause is what it's for. Its formal cause is its structure, the arrangement of relationships, authority, space, money and speech that makes it the kind of thing it is.
In one sentence, the argument of intra-ecclesial apologetics is that the modern church has kept its material cause and its efficient cause and changed its formal cause. It has the same people, the same gospel and the same Spirit, arranged in a different form.
On this analysis that is no trivial change. Form is what makes a thing the kind of thing it is. It's tempting to call recast bronze the same object with a new appearance, but it is a different object made of the same stuff.
Substantial and accidental form
Aquinas distinguishes changes that leave a thing what it is from changes that make it something else. A man who tans, ages, or learns Greek is still the same man, because those are accidental changes. A change of substantial form is a change of kind.
For the church, the question becomes which changes to its form are accidental and which are substantial. What Scripture mandates is substantial form. If you remove the reciprocal commands, participatory edification, plural eldership, mutual correction, care for the poor and hospitality, the thing becomes a different kind of thing, whatever it's called. What Scripture models or leaves free, such as meeting times, buildings, music and language, is accidental form, real and sometimes important and still changeable without the thing ceasing to be itself.
The distinction between mandated and free applies a metaphysical distinction that has been in use for two and a half thousand years to a particular kind of thing, so it is more than a hermeneutical convenience. The consequence is blunt. When a body has lost enough of the substantial form, "a worse church" no longer describes it. It has become a different kind of institution that retains the name.
Action follows being
The principle that grounds the method is a scholastic tag, agere sequitur esse, action follows being. A thing acts according to what it is. Its operations follow from its form.
If you want different operations, then, you need a different form. Exhortation addressed to a thing whose form produces the current operations is asking it to act against its own nature.
Every finding about congregations is measuring this one principle. The setting predicts behavior better than the person does, a room built for an audience produces an audience, and a role with no real work produces no ownership. In each case action follows being. The structural argument is a classical claim, stated by Aquinas, that modern research has spent a century confirming. Theology didn't import it from sociology.
It also explains why the standard response to poor fruit doesn't work. More sermons, more conviction and more sincerity all address the will of the members. A thing acts according to what it is, and none of them touches the form of the thing.
The cause of causes
The final cause explains the other three. A saw is made of iron because of what a saw is for, and its shape is as it is for the same reason, so a thing's form is evidence of the end it actually serves.
That gives a diagnostic. Look at what a congregation's form is fitted to, and read the end off the form, whatever the congregation says it's for. A body arranged around a weekly produced event, in a room built for an audience, funded to maintain a plant and staff, measured by attendance, has a form explicable by a particular end. It may not be the end anyone would state.
And where a form is fitted to an end nobody intended, somebody else did the arranging. The whole history of the church's captivity to its host cultures is a story of that kind, with the form shaped by Greece, Rome, Europe and America. Nobody in the pews chose it.
Where God is in this
That brings me back to the objection and the question of where God is in all this. He is, first, in the principle itself. Grace perfects nature means God's action works through the creature's nature, so studying the nature is studying the medium of grace.
Second, he is in the design. The commands, the household form and the reciprocal obligations are given, and nobody worked them out as a human strategy for spiritual results, because the Spirit prescribed them through the apostles. Taking the design seriously is taking divine agency seriously at the point where it's most concrete.
Third, he is in the means. Aquinas's account is that God uses sensible things because it's natural to human beings to reach the intelligible through the sensible, so his is a theology of God working through created means like water, bread, wine, hands, rooms, meals and neighbors.
Fourth, the texts say so directly.
I have planted, Apollos watered; but God gave the increase. So then neither is he that planteth any thing, neither he that watereth; but God that giveth the increase. (1 Corinthians 3:6-7)
Two human agents do deliberate, skilled, structural work, and the growth is attributed entirely to God. Paul says the planting wasn't the cause. He never calls it unnecessary. The design assumes both are true.
And after the apostles restructure the Jerusalem church in Acts 6, delegating the distribution and protecting prayer and the word, Luke's next sentence is: And the word of God increased; and the number of the disciples multiplied in Jerusalem greatly (Acts 6:7). The administrative decision and the divine result sit in consecutive verses, with no embarrassment about the connection.
Privation: why the diagnosis stays charitable
One last idea from Aquinas keeps this discipline from becoming an accusation.
Evil, he held, has no positive existence. It is a privation, the absence of a good that ought to be present. In blindness nothing positively evil has been put into the eye. The eye lacks a perfection eyes ought to have.
That category is exactly right for a deformed congregation, which is a good thing lacking a form it ought to have. Wicked is the wrong word for it. Nothing is wrong with the people or the gospel, and the Spirit isn't absent, but a perfection that ought to be present is missing. The members feel the absence directly and can't name it, because a privation has no positive features and nothing to point at.
That's why so many believers ache without being able to say why. A bad thing could be named, but what they're experiencing is the absence of a good one. The work of intra-ecclesial apologetics is to give the privation a name, so that the thing lacking can be identified and then supplied.
Far from being a license to do sociology in place of theology, grace perfects nature is the theological claim that makes the sociology relevant.