A heresy trial over baptism

Reformed theologian Peter Leithart is in trouble again over his views on baptism.  He was tried by the Presbyterian Church in America and found innocent of doctrinal violations, but when the prosecutor in that case recently converted to Catholicism, the church body is questioning that decision and looks to put Rev. Leithart back on trial.   (So double jeopardy doesn’t apply to church trials?)  I am in no position to know whether his position is in accord with PCA doctrine or not, but I am curious about the extent to which it accords with Lutheran doctrine.  I’ll post his statement of his beliefs after the jump.

From Primer on baptism » Peter Leithart | A First Things Blog:

First, we should take the Bible’s statements about baptism as statements about baptism. Through Paul, God says that those who have been baptized are dead and buried with Christ (Romans 6:4) and that as many as have been baptized into Christ are clothed in Christ (Galatians 3:28-29). By analogy with the exodus, Paul implies that those who are baptized are rescued from Egypt and baptized into Christ, the new Moses (1 Corinthians 10:1-4). Peter tells his hearers at Pentecost to repent and be baptized “for the remission of your sins” (Acts 2:38) and says “baptism now saves you” (1 Peter 3:21). We can choose to disbelieve these things, or explain them away, but that’s what these texts say. I submit that we should believe what God has to say on the subject of baptism. That’s the starting point. When the Bible speaks about baptism, it is speaking about the rite of baptism; and what it says is true.

But how can we say this? We know that not everyone who is baptized is saved. We know that not all baptized people even profess to believe. The New Testament speaks this way about baptism, I have argued, because of what it teaches concerning the church.

What it teaches is that the visible church is the body of Christ; Head and body form a single reality that Paul is willing to describe as “Christ” (1 Corinthians 12:12). That is a metaphor, but not merely a metaphor. The church consists of those people who have been joined to the incarnate Son by His Spirit, the Spirit active in Word and Sacrament. Since the church is a divine-human society, since it is that kind of community, it is impossible for membership in the visible church to be merely external, social, or legal. If you are baptized into the body, you are baptized into a real union with the incarnate Son. You are a son in the Son.

Yet, of course, not everyone who is united to Christ in His body perseveres. Those who fail to persevere ultimately fail because they are reprobate. They eventually grieve the Spirit and fall away, showing themselves to be rebellious sons. But in the meantime, while they share in the life of the body of the Son of God, they share in various ways in the gifts of Christ through His Spirit (cf. Hebrews 6:4-6; 2 Peter 2:17-22).

My sense is that this may violate the Calvinist understanding of Perseverance of the Saints, but not, perhaps, the Lutheran understanding, which teaches the assurance of salvation (to be found, among other places, in baptism), but that salvation can, in fact, be lost (which explains why some who have been baptized no longer believe).   But what do you think of Leithart’s theology of baptism?  How is it similar to and/or different from the Lutheran theology?