There's an objection that any serious Christian will raise against the whole project of studying the church's structure. It goes like this: Where is God in this? Attachment, group dynamics, architecture, incentives — is formation being reduced to social engineering? Has the Holy Spirit been replaced by a floor plan?
The objection deserves a direct answer, and the best answer comes from a theologian who spent his life on exactly this question: Thomas Aquinas, and his principle that grace does not destroy nature; it perfects it.
What the principle means
Aquinas's claim is that God's saving action doesn't bypass the creature's nature but works through it. When God makes a person holy, he doesn't replace that person's humanity with something else. He heals it, elevates it, and brings it to what it was made to be. Grace presupposes nature — 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, not around it. 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. It isn't Aquinas's theology, and it isn't the New Testament's.
Scripture says exactly this:
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's 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 doesn't plant isolated converts. He plants households.
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: what it's made of. The efficient cause: what brought it about. The formal cause: what makes it the kind of thing it is — its structure, its arrangement. And the final cause: what it's for.
A bronze statue is the standard illustration. Its material cause is bronze. Its efficient cause is the sculptor. Its final cause is the honoring of someone. Its formal cause is the shape — because 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. Its final cause is what it's for. And its formal cause is its structure — the arrangement of relationships, authority, space, money, and speech that makes it the kind of thing it is.
This is the argument of intra-ecclesial apologetics in one sentence: the modern church has kept its material cause and its efficient cause and changed its formal cause. Same people. Same gospel. Same Spirit. A different form.
On this analysis that isn't a trivial change. Form is what makes a thing the kind of thing it is. Bronze that has been recast isn't the same object with a new appearance. It's a different object made of the same stuff.
Substantial and accidental form
Aquinas distinguishes changes that leave a thing what it's from changes that make it something else. A man who tans, ages, or learns Greek is still the same man — these are accidental changes. A change of substantial form is a change of kind.
The question for the church becomes precise: which changes to its form are accidental, and which are substantial?
What Scripture mandates is substantial form. The reciprocal commands, participatory edification, plural eldership, mutual correction, care for the poor, hospitality — remove these and the thing is a different kind of thing, whatever it's called. What Scripture models or leaves free — meeting times, buildings, music, language — is accidental form: real, sometimes important, and changeable without the thing ceasing to be itself.
This is why the distinction between mandated and free isn't a hermeneutical convenience. It's the application of a metaphysical distinction that has been in use for two and a half thousand years, to a particular kind of thing. And it has a blunt consequence: a body that has lost enough of the substantial form hasn't become a worse church. It has become a different kind of institution that retains the name.
Action follows being
Next is the principle that grounds the method. A scholastic tag: agere sequitur esse — action follows being. A thing acts according to what it is. Its operations follow from its form.
That means: if you want different operations, 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 — that the setting predicts behavior better than the person, that a room built for an audience produces an audience, that a role with no real work produces no ownership — is measuring this one principle. Action follows being. The structural argument isn't a sociological import into theology. It's a classical claim, stated by Aquinas, that modern research has spent a century confirming.
It also explains why the standard response to poor fruit doesn't work. More sermons, more conviction, more sincerity — all of these address the will of the members and none of them touches the form of the thing. And a thing acts according to what it is.
The cause of causes
The final cause explains the other three. A saw is made of iron because of what a saw is for. Its shape is as it's because of what it's for. So a thing's form is evidence of the end it actually serves.
That gives a diagnostic. Don't ask a congregation what it's for. Look at what its form is fitted to, and read the end off the form. 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 — and 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. That's the whole history of the church's captivity to its host cultures: the form was shaped by Greece, Rome, Europe, and America, and nobody in the pews chose it.
Where God is in this
So, the objection. Where is God?
First: in the principle itself. Grace perfects nature means God's action works through the creature's nature. Studying the nature is studying the medium of grace.
Second: in the design. The commands, the household form, the reciprocal obligations — these are given. They aren't a human strategy for spiritual results. They're what the Spirit, through the apostles, prescribed. Taking the design seriously is taking divine agency seriously at the point where it's most concrete.
Third: in the means. Aquinas's account of why God uses sensible things — because it's natural to human beings to reach the intelligible through the sensible — is a theology of God working through created means. Water, bread, wine, hands, rooms, meals, neighbors.
And fourth: the texts say so directly.
I've 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 doing deliberate, skilled, structural work — and the growth attributed entirely to God. Paul doesn't say the planting was unnecessary. He says it wasn't the cause. Both are true, and the design assumes both.
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). An administrative decision and a divine result, in consecutive verses, with no embarrassment about the connection.
Privation: why the diagnosis stays charitable
One last thing from Aquinas, and it keeps this discipline from becoming an accusation.
Evil, he held, isn't a thing. It has no positive existence. It's a privation — the absence of a good that ought to be present. Blindness isn't a positively evil something in an eye. It's an eye lacking a perfection eyes ought to have.
That category is exactly right for a deformed congregation. It isn't a wicked thing. It's a good thing lacking a form it ought to have. The people aren't defective; the gospel isn't defective; the Spirit isn't absent. A perfection that ought to be present is missing — and 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. They aren't experiencing a bad thing. They're experiencing the absence of a good one. And the work of intra-ecclesial apologetics is to give the privation a name, so that the thing lacking can be identified — and supplied.
Grace perfects nature isn't a license to do sociology instead of theology. It's the theological claim that makes the sociology relevant.