The Gospel Coalition has a series of installments answering theological questions that are emailed to them. The most recent installment has Luke Stamps, a professor at California Baptist University, addressing a question that was submitted regarding whether Christ assumed a fallen human nature -- the view of Protestant luminaries Barth and Torrance, as well as that of the Orthodox Church.
The piece essentially answers the question in the negative: there are too many 'problems' with the view that Christ assumed a fallen human nature (and therefore, full human nature as it actually exists). Stamps does at least acknowledge the validity of the motivation for adopting the view but ultimately rejects it. He gives a series of reasons for rejecting it, though they all ultimately hinge on the fact that "the mainstream Reformed understanding of original sin [is that] to possess a fallen nature is to be guilty before God." But this amounts to question-begging. The very question at hand is whether this view of original sin is correct.
In Stamps' first reason for rejecting the view, he says that fallenness is not an essential feature of human nature as such, but rather a result of the fall. "Fallenness is a not a 'part' of humanity that must be healed." While it's true that fallenness is not an eternal feature of human nature, it is still an aspect of human nature post-Fall and outside of union with Christ. Stamps is positing human nature as a static, eternal thing rather than something subject to change, and he does so without any justification given.
His second reason is the one that directly invokes the Reformed understanding of original sin, and as such is the one that makes the least sense. "Presumably 'fallenness' in [the FHN] context means possessing a propensity
toward sin, even if no actual sin is committed. But how could a human
being in this state not be condemnable in the eyes of a holy God?" His question seems to answer itself. How can God neglect to find something condemnable which is not worthy of condemnation? If your premises force you to ask such questions, it's time to re-examine your premises.
The third objection appeals to a christological conundrum that doesn't actually exist. Stamps asks "how could the infallible Son of God be joined to a morally fallen human nature?" Could one not also ask how the uncircumscribable God could become circumscribed in the womb of the Virgin? Or how the infinite God became finite? Or how the impassible God suffered on the Cross? Are any of these mysteries of the Incarnation any less irresolvable for us? Unless you're rejecting the Incarnation itself as self-contradictory on rationalist grounds -- which no Christian is permitted to do -- then this just is not a difficulty. Further, it calls into question the necessity of, for example, the Cross. If Christ has taken on pre-Fall human nature only, then is the 'flesh' of fallen man really being crucified at the cross? And if not, what good does it do us who indeed possess a fallen human nature?
He goes on to make a specious distinction between the scripturally undeniable "fallen experience" of Christ and taking on a fallen human nature. If Christ is just dwelling amongst fallenness as a passer-through, and not taking it into himself, then how is it that our salvation is affected?
Stamps quotes St. Gregory the Theologian's maxim that "that which is not assumed is not healed." Just so.