Mason Tarwater's Implicit Augustinianism

In The Violent Bear It Away, Flannery O'Connor's second novel, the main character, Mason Tarwater, is a decidedly independent prophetic figure with a history of kidnapping child relatives to preach to them. Not your best example of a good pastor. But he did understand something about baptism:

As a lone prophet who belongs to no visible church, the proclaimer of a radically communal kingdom appears to be a contradiction in terms. Yet he recognizes that, unlike any benefit the world might bestow, the baptism of his two nephews will make them members of the universal Christian family, his kinsmen in faith far more than blood. Just as one does not elect one's parents, neither can one choose God as the ultimate parent. The triune Lord sovereignly wills not to confine his communal life within the Godhead but to gather a people unto himself. Even when baptism is a freely chosen deed rather than the decision of parents and godparents, it signifies much more than one's own decision to follow Jesus. Baptism is for Christians what circumcision is for Jews: a public sign that the universal God of Israel and Christ and the church has claimed believers for life in a particular community that lives by its outward and visible practices. Baptism is thus a political act through and through: it is a radical transfer of allegiance and citizenship from one regime to another, from a polity that is corrupt and perishing to the only one that is being redeemed and shall stand forever. Not even the gates of hell will be able to prevail against its onrushing power. Baptism is a sacramental and regenerative rite precisely because it is not a merely human choice; it is God's own adoption of his people into his community.

St. Augustine learned this difficult truth in the summer of 382, after he had embraced a neo-Platonic kind of Christianity but remained undecided about his baptism. He recalled the story of two friends who had disputed this very question. Victorinus had mastered the Scriptures and studied all the Christian books, yet Simplicianus insisted that he would not consider him a Christian until he was baptized into Christ's body. "Then do walls make Christians?" Victorinus impatiently and perhaps mockingly asked. The popular assumption of our time, shared by many Catholics no less than most Protestants, is that the answer is negative. The future bishop of Hippo, by contrast, remembered this story because he knew that Simplicianus required a positive response. The walls of the church -- a metaphor for Christ's visible and earthly body -- do in fact make Christians.

--from Chapter 7 -- Vocation: The Divine Summons to Drastic Witness