In my response to Frank Beckwith and John Mark Reynolds in The City, I pointed out that any that Christendom is impossible until evangelicals recover a robust notion of the Church's existence as a culture--and maybe not even then. The notion of Church as culture, though, begs the difficult and tangled question of what kind of culture the Church is?
This is one question Peter Leithart raises in his brilliant little book, The Baptized Body. Leithart defends baptizing infants by locating the practice in the context of discipleship and full integration into the culture that is the Church. Writes Leithart:
If the church is indeed a culture, then instilling Christian character is analogous to instilling character in other cultures. Groups display common characteristics not so much because of genetics and racial characteristics, though these factors should not be wholly discounted; primarily, individuals display the character common to their group because they have been nurtured in common habits, outlooks, aspirations, hopes. They have learned a common language, see their own lives and history in general in terms of a common story, and have a common outlook on life.
I will not recount the full argument here, but one aspect of Leithart's defense of infant baptism has, I think, particular bearing on our understanding of the Church. Leithart points out that "infant baptism imposes a religious identity that the infant has not chosen." Leithart argues forcefully against the adult baptist position that infant baptism indicates "not absolute choice, but an alternative givenness, equally unchosen."
Though Oliver O'Donovan does not interact explicitly with Leithart's essay, he might as well have, as his treatment of the question of baptism in Desire of the Nations has substantive overlap with Leithart's:
Baptism is the sign that marks the gathering community. It was the sign that marked the community when Jesus himself accepted it; for he came to be baptized by John as the representative of God's expectant people. In accepting baptism, each new believer accepts Jesus as his or her representative, and accepts Jesus' people as his or her people...We say 'each' new believer because existing collective identities have to be set aside and replaced with this new collective identity. Even members of existing Israel had to come out to the wilderness to find God's Israel there. In baptism each person makes vows singly, is addressed singly and (by tradition) given a new name. The prophets of the exile expected that the gathering to Jerusalem must take place one by one (Isa 27:12, cf. Jer. 3:14).
O'Donovan's notes on the matter are worth excerpting as well, for he expands his critique of Protestant defenses of infant baptism:
The characteristic weakness of defences of infant baptism is that they elide this point. The defence which has most influenced Protestant thinking, that of John Calvin, is a clear example. Taking as its starting-point the apostle's comparison of baptism and circumcision in Colossians 2:11f., it draws from this an analogy between the membership of Israel and the membership of teh church. This overlooks precisely the most important difference between Israel and the church as political societies. As the eschatological society, the church is entered only by leaving other, existing socities. It is not a society anyone can be born into. There is a better way to understand the traditional practice. Because the community is eschatological, the decision of a person to enter it is not one among many decisions; it is the one, total and final decision of life. For this reason no person may be baptised twice. If the virtue of adult baptism is that it throws weight upon the personal decision of the candidate, its danger is that it invites confusion between the particular decision to be baptised and the ultimate decision which baptism represents. That decision is not taken on a Wednesday! Infant baptism, on the other hand, by locating the sign at a moment when there is no possible particular decision to confuse it with, throws into high relief the eschatological character of the decision to follow Christ. Yet it is still the candidate's decision, and no one else's, that is treated of.
Sociologically speaking, the renewed emphasis on the continuity between creation and new creation is behind both the rise of the young Reformed and the progressive elements of evangelicalism that are focused on social justice. Leithart's appeal to the analogy between the culture of the Church and other cultures seems to rest upon this continuity, which perhaps is why I am more in line with O'Donovan on this point: the reality of the resurrection introduces discontinuity in the structure of creation and makes the Church a community unlike any other in such ways that the individuality of choice must be given its place.
But evangelicalism and our historical emphasis on voluntariety need to be chastened by Leithart's argument that the reality of our salvation precedes our conscious response, and that our choice is not determinative of salvation. As O'Donovan writes elsewhere, ""The subject is realized in the church, the church completed in the subject."