Leithart writes:

After the Reformation, Reformed churches found themselves striving not only with Catholics but with Lutherans, and as a result both Reformed and Lutheran dogmatics developed along the lines of a one-sided, though historically understandable, via negativa. Reformed theology had its own resources on which to draw, but at many points, and particularly on issues of ecclesiology and sacraments, defined itself as not-Lutheran and not-Catholic. Lutherans did the same. My church history professor at seminary said that Lutheran dogmatics texts had a threefold structure: The Catholic Error, the Reformed Error, and the Lutheran Truth. Reformed theologians followed (and some still follow) a similar method. Reformed theologians and churches, as a result, formed their identity as Reformed by distinguishing their views and practices from Lutherans and Catholics. In the wake of the fundamentalist controversy, Presbyterians added another element to this theological method – we are not-liberals. The badge of inclusion in the Reformed world was not teaching any form of baptismal regeneration.

“Federal Vision” theology messes with these boundaries. It attempts to follow the lead of Scripture, even when that seems to conflict with Confessional formulae and seems closer to Luther than Reformed orthodoxy. It develops a baptismal theology that is not starkly at odds with Luther, appreciates de Lubac on the doctrine of the church and Alexander Schmemann on the Eucharist, finds Barth and Lindbeck intriguing and helpful at a number of points, and is stimulated by Anglican New Testament scholar N. T. Wright. As a result, “Federal Vision” theology challenges conservative Reformed culture as much or more than it does Reformed theology, for it questions the performances and boundaries that once defined this culture. Though the specifics of the debate can appear to be so much gnat-straining (particularly to those few outside the Reformed world who pay attention), the debate touches a nerve and provokes profound reactions because it’s not just a theological debate but an identity crisis. The Federal Vision challenges some of the identifying symbols, the boundary-markers of Reformed communal identity, and that kind of challenge cannot help but provoke a heated response.

From this angle, the future shape of American Presbyterian will be significantly shaped by the outcome of this debate. It appears to me that one of the issues facing the OPC and the PCA is whether we will isolate ourselves in an ever-more enclosed sectarian form of Christianity or whether we will more and more see ourselves as a distinctive stream of the catholic church.

More or less on target, it seems to me.