There is an interesting blog discussion here on Pastor Weedon’s blog. You need to go past the blog itself, and into the comments string to get the full force of it.
Basically, it is a question of the Real or Imputed Righteousness. Catholics claim the former, Lutherans the latter. The point at issue is a quotation from St Augustine, ostensibly misquoted in the Lutheran Confessions. Bryce Wandry tells this story:
Professor Richard Rex wrote: “For in the Lutheran tradition, the definition of the concupiscence of the flesh after baptism as sin has been constantly and confidently attributed to Augustine, specifically to his treatise De nuptiis et concupiscentia, and this is demonstrably wrong.”
And so, in the Apology, defending Luther’s view, Melanchthon writes, “Sin is forgiven in Baptism, not that it no longer is, but it is not imputed.” [Rex uses Tappert and gives the page number 105]. And so Rex says further, “So I went back to the Patrolgia Latina, which follows the Benedictine edition based on a wide range of Roman and French manuscripts, to find the following words: ‘If somebody asks … why, if this concupiscence of the flesh can remain in the baptised parent and not be sin, it can still be sin in the offspring: the answer is, that concupiscence of the flesh is remitted in baptism not so that it is not, but so that it is not accounted as sin.’ (PL 44.430).
And so Rex concludes, “If we take the trouble to verify this crucial citation, we find that it is the Catholic doctrine, not the Lutheran doctrine, that derives from Augustine. And since Augustine in effect invented the theological concept of original sin, I believe that we are perfectly justified in accepting his account of it rather than Luther’s.”
There then follows (in the discussion string) a long question of whether indeed Augustine’s words, highlighted in bold above, defend the Catholic doctrine or the Lutheran one. Here are my comments:
Let’s return to Augustine’s original question about how children born of baptised parents are born in original sin, because it is an important one. From Augustine’s answer, we can derive that:
1) Baptism renders the concupiscence “not sin”. The concupiscence that remains after baptism is not sin–not in any sense at all, proper or improper. This is what Augustine means when he says “it is not accounted as sin”. Not “It is sin, but God decides not to count it as sin”, but “It is not sin, and therefore is not accounted as sin”.
2) There are two types of sin (original and actual) not three (+ concupiscence). Correct me if I am wrong, but in Augustine’s thought concupiscence is the bearer of original sin which gives rise to actual sin. As all are conceived of parents who are concupiscent (even parents who have been baptised and therefore are free of original sin), the one conceived is born concupiscent, and (until baptised) with the accompanying result of original sin.
3) Baptism alone renders concupiscence “not sin”. Unlike original sin, purity from sin cannot be inherited by offspring through conception. Christ did not receive his purity from sin from his immaculate mother; on the contrary, she received her immaculate condition from him. Without baptism, concupiscence carries original sin and leads to actual sin.
Hence Augustine is speaking of real and not simply imputed righteousness after sin.
Does that make sense?