I read through all the links posted in the OP.
I agree with some of what Heiser says and disagree with some of what he says.
Here are some extended copy/pastes from "More on Romans 5:12 (Part 3)" that I think get to the heart of Heiser's argument.
Now let’s take a look at the verse. I ask you: are you going to base your theology on what the text actually says, or what you’ve been told to see in it? What does the Scripture say?
“therefore, just as sin came into the world through one man”
• Adam’s was the first sin
“and death through sin”
• What did Adam’s sin bring? Death.
“and so death spread to all men”
• Does the text say “so that ADAM’S GUILT” passed upon all humankind? NO, it does not. The ONLY thing that the text says passed on to all humankind was DEATH. It’s quite clear and explicit. To say “guilt” is to import the idea into the text. This is eisegesis.
“because / so that all sinned”
• Here’s an important element. The English conjunction here is actually a translation of a Greek preposition (epi) + a relative pronoun. That combination can denote cause (“because”) or result (“so that”), as well as meanings like “upon which” (where/location) and “on behalf of”.
• If we take “because” then what we have is that the verse tells us that the REASON all humans dies is because all sinned. This is the Augustinian view, but that is contrary to reality. All humans were not “in” Adam. We share genetic characteristics, but genetic traits are not PEOPLE or PERSONS. For the Augustinian view to work, you must have PERSONS in Adam, since it is PERSONS, who incur guilt, not traits! (There are no genetic traits in hell; genetic traits weren’t atoned for by Christ – PEOPLE are and were).
• If we take “so that”, then the verse sounds a bit odd: “everyone sins because death spread to all men.” That’s actually not weird when you look at it this way: “everyone sins because THEY ARE MORTAL.” This is also part of my view below, so take your pick of translation here!
Here’s my take.
1. I believe Romans 5:12 teaches that Adam sinned, and HE became guilty before God. His guilt was his own, not ours. It wasn’t his guilt that was transferred to all humans. It was something else. I believe Scripture is clear that Adam sinned, and that something happened to the rest of humanity born from that point on, but that something is NOT the transmission of guilt before God. If it was, then Jesus was guilty before God since he is fully human and in Adam’s line.
2. That something *produced* the conditions by which all humans will become guilty before God *on their own* and in need of Savior.
3. What passed to all of humanity as a result of Adam’s sin was mortality / death. That is what the text says. This means that humanity lost immortality. It also means, going back to the Genesis story, that humans were driven from the presence of God in an ideal “heaven meets earth” environment. They were on their own. Left to their own, as non-divine mortals, the result is that all humans, born from that point on, were born into those conditions. If they are allowed to live a normal life span, this means that all humans will sin and incur guilt before God. No human “cannot not sin.” Sin would be universal and inevitable for all humans who get to live some measure of a lifespan where they can choose to rebel against God (i.e., sin).
4. In other words, mortality = the universal propensity and inevitability of sin. All humans need Christ and his work for salvation.
5. This in turn is the answer to the Jesus dilemma. YES, Jesus inherited Adam’s fall – because all that means is that he inherited MORTALITY. And of course Jesus was mortal in the incarnation. He COULD and obviously DID die – like any other human, barring divine intervention (like Elijah and Enoch). Jesus didn’t inherit guilt from Adam because that isn’t the point of Romans 5:12. There is no dilemma.
All this has some important ramifications. It means there are humans who never sin and who never become guilty before God, though mortal. Who am I talking about with the plural? Aborted babies, still born babies, spontaneously aborted humans after conception, the severely retarded, etc. They never incur guilt before God. One needs to actually sin, and sin involves the will (it is different than OT profanation of sacred space, defilement by another, and the need for RITUAL cleanness in the wake of unintentional defilement). We tend to wrap all those things into one because we don’t live in a ritual culture, or practice religious cult, with its notion of sacred space and holiness of inanimate objects (etc.) like Israelites did. It’s foreign to us. There’s a difference between violation of ritual space, like in the OT, and moral guilt — deliberate violation of divinely-given morality / rules of conduct, and even theology. (And this last element (theology) has more to do with worshipping another deity and rejection of the nature and character of the true God than getting every doctrinal principle right). Both are “sin” (i.e., transgression), but they are characterized differently. As Paul noted, Eve was deceived, but Adam sinned willfully — and so it is HIS violation that triggers the advent of death upon all humanity. For our purposes, then, people go to hell because they (1) incur moral guilty before God and (2) that moral guilt is never removed through the work of Christ. If you are never guilty before God, you don’t have that problem – but you still don’t have what it takes for heaven. The basis for eternal life is still (and can only be) Christ and his work.