I think I concur with Craig that the traditional understanding is that Adam's sin is imputed as Christ's righteousness is imputed. But --in addition--, Adam's sin corrupted his posterity horribly.
A careful exegesis of Romans 5:12-19 will bear this out, showing that -at root- we are condemned in Adam (but -additionally- we are condemned for our own sins. (John Piper in his powerful recent book, "Counted Righteous in Christ", carefully unfolds this idea and imputation in general...)
I have read Piper's book, and in particular the discussion on Rom. 5:12-19 in question. I must confess, I always find it hard to pin-down exactly what Piper is trying to say. But the issue at hand is whether we are charged with Adam’s sin, as if we committed it, or whether the "only" way in which Adam’s sin condemns us is because his sin resulted in the ruination of mankind—which in turn means we are born sinners, condemned for our own sins (Rom 5:12: "… because all sinned.") I think Piper pushes for a perfect symmetry between the imputation of Adam's sin and Christ's righteousness, in spite of the fact that the very text he uses actually points out differences (v. 15-16). Piper paraphrases the text to make it a better fit for his thesis.
Piper doesn't want us to stand condemned "only" because all have sinned individually, because it would necessarily follow that we are justified and are given life in Christ because all commit righteous acts individually. Here he is assuming his conclusion, that the imputation of Adam's sin to us is "just like" Christ’s righteousness to us, and so if we are "only" condemned because of our own sin then we are “only” righteous because of our own righteous acts. He may be right, but not because his logic is inescapable.
Just to point out a couple thoughts, not necessarily meant to be convicting:
- There is a sense in which this is academic, for all (Reformed) agree that we are born totally corrupted and will in fact condemn ourselves from conception. In other words, being charged with Adam's sin is somewhat superfluous. The issue, as Piper would agree, is really whether it affords a deeper understanding of imputed righteousness.
- On the other hand, we can ask the following question. What would it say about God's character if the imputation of Adam's sin is in the same manner as the imputation of Christ's righteousness to us and the imputation of our sins to Christ? The latter, our sins to Christ, is not unjust for Christ because He voluntarily took the punishment for our sins, which renders the atonement an act of pure mercy and love for us, and not injustice to Christ because He accepted the imputation. We, by contrast, have not agreed to be punished for Adam's sin. God can do whatever He wants except act in a manner contrary to His own character. If we are viewed by God as if we committed Adam's sin, even to the point where we are condemned as if we had committed it, then is not God unjust? I say yes, it would make God unjust. But if we are condemned for our own sins, made inevitable as a result of the fall (so in that sense we all are condemned through our representative Adam) then God is just in His condemnation.
As always, human analogies are dangerous. But we do not imprison a man for his father's crime. And when lousy parenting produces a criminal, we punish the criminal for his crimes, even though it may be argued that his parents doomed him through their own mistakes.
Piper uses Jonathan Edwards to support his claim, but Edwards is also difficult (although less so than Piper) to understand unambiguously. What Edwards wrote, in my opinion, is consistent with my position. Yes, Adam's sin is imputed to us as and is manifested in the depravity of our heart. And yes, God is just in corrupting mankind because of Adam's sin, for in a sense Adam fell and then the human race was polluted through him. But I do not think that Edwards ever writes that Adam's sin is a first cause, as opposed to an indirect cause, of the condemnation of a lost soul.
It would be interesting if some of the Reformed blogo-scholars such as this guy and that guy (and others) commented on this question, as well as that knowledgeable Lutheran misanthrope. The latter has not recently accused me of partaking of illegal medications, so I am worried that I am losing whatever edge I once had.