There are various ways of talking about original sin and the fall of man within Christianity. One of the most difficult for modern people to understand is the legalistic language which is quite common amongst Roman Christians. Having recently explained it on Twitter, I’m going to re-present that explanation here, more coherently.
The key to understanding inherited guilt in the legalistic framework is the concept of guilt within the legalistic framework is not identical with the common understanding of guilt one finds today. The problem is that the modern understanding of an individual is as an atom, utterly unconnected from anyone else. Guilt, then, is taken as a moral judgment of the individual more-or-less as a proxy for the final judgment on Judgment Day (at the end of time).
Guilt within the legalistic framework is only concerned with the justice of a punishment. Now, punishment is in all cases some sort of deprivation—whether it’s the imprisonment of a man which deprives him of his freedom or the removal of his hand which deprives him of his hand or the removal of his head which deprives him of his life. But these are all individual punishments, which can only be just when they re-balance some sin of the offender himself.
There are also corporate punishments, which punish groups, but we tend not to be familiar with them because the atomized view of the individual prevents us from recognizing corporate goods. So we have to start there.
Inheritance is the natural order of things; children are supposed to inherit the possessions of their parents. As such, a man does not really own anything himself; it is owned by his family and he keeps it in trust for his descendants. Moderns will rebel against this, but there’s really nothing to be done about that because they are, simply, wrong. Human beings are not merely members of a group, but they are not merely individuals, either. This is just a more extreme but more common form of when people tell police officers that they are sovereign over themselves and not citizens and thus may not be detained by the police. Great theory, just not true.
Depriving a man of goods—as in, for example, the seizing of land, though even just a fine of money is the same in theory—is a punishment not merely of the man but of all his descendants, too, since taking it from him is also taking it from them. The natural order of inheritance is being broken, and this demands some justification. Why may the descendants be deprived of what is theirs by the natural order of things? By what right does one punish the descendants as well as the wrongdoer?
And this is where the concept of inherited guilt comes into play. If it is just to deprive the descendants of a wrongdoer of some good, it means, by definition, that they are guilty. Recall that the definition of guilt, within a legal framework, is nothing other than the infliction of a punishment being just. If the infliction of a punishment is just, it is, therefore, being guilty (in this sense). And when one asks where the guilt came from, it must have come from the same ancestor who did the wrong; that is, just as one should have inherited the good, one may inherit the guilt which makes the not-inheriting of the good just.
Within the legalistic framework, if the guilt were not inherited it would be unjust to not restore the property to the wrongdoer’s descendants.
It is easy to see where confusion arises in the modern world because people, hearing the word “guilt” cannot help but think this refers to the state of the man’s soul on judgment day. But this is not what is meant; what is meant is what is just to the man here and now.
When Romans, writing legalistic explanations of theology, talk about our inherited guilt from Adam, this is what they are referring to—the justice of our present deprivations.
It should also be noted that this is quite different from mercy, which is giving to a man more than what he justly deserves. This is also a problem in the modern world because moderns are not used to the idea of considering two ideas at once. We have become so accustomed to demanding the bottom line that considering both obligations and generosity is—almost literally—unthinkable.