I just finished reading a really provocative and intriguing essay by Ho-Jin Ahn in the Scottish Journal of Theology. In it he takes Oliver Crisp to task (at least at the ground clearing level) on Crisp’s argument that Christ could not have assumed a fallen sinful humanity in the incarnation; since according to Crisp (and the scholastic [speculative] tradition from which he argues), if Christ truly took on a depraved humanity, then he would have needed a Savior himself. Ahn helpfully relocates Crisp’s placement of this discussion from the Augustinian “original sin,” and moves it into the realm of Christology (which is where this dialogue ought to take place!). Ahn, in the process of relocating this discussion, develops John Calvin’s understanding on this issue; Ahn looks, in a dialectical way, at Calvin’s commentaries and his Institute. In a nutshell, what Ahn concludes is that Calvin might ‘appear’ to hold to something like Crisp (that Christ assumed an unfallen human nature), but in the final analysis, and at an interpretive/functional level, Calvin thinks from a view that sees Christ entering into the depths of our fallen humanity and redeeming us from the inside out through his vicarious humanity for us. Here is Ahn’s conclusion:
It is unreasonable for some theologians to argue for Christ’s unfallen humanity in the context of the doctrine of original sin because Christ himself overcame the power of sin and death in his fallen humanity. In the case of Calvin’s understanding of Christ’s humanity, we see that there is a tension between the nature and the state of Christ’s person. Calvin believes that Christ assumed our true humanity, lived a perfect life, and was sinless according to the Chalcedonian Definition. Thus, Calvin denies the fallenness of Christ’s humanity in order to preserve the doctrine of Christ’s perfect innocence. However, unlike others who are in favour of Christ’s unfallen humanity, Calvin forcefully affirms the vicarious humanity of Christ in our corrupted state. Calvin affirms that Christ had to suffer from our existential problems according to the narratives of the Gospels. Moreover, the mortal human nature which Christ assumed shows solidarity with sinners and the vicarious humanity of Christ pro nobis. If Calvin were to accept the idea of the fallen nature of Christ, his thoughts on Christ’s humanity for us would be more persuasive. Yet it is noted that Calvin’s theological logic is ‘anti-speculative’ in that he focuses on what Christ has done for us in his true humanity.
Nevertheless, Calvin argues that the body of Christ himself is the temple of God through which we can come to the throne of God’s grace. Although Christ assumed our mortal body controlled by the power of sin and death after the Fall, Christ sanctified the body in his own person as the Mediator between God and all the fallen humanity and decaying creation. Furthermore, the reconciliation with God is not just attributed to the crucifixion of Christ in an external and forensic way but to the perfectly holy life of Christ who assumed our mortal body as a saviour in an internal and ontological perspective. Calvin’ s biblical views on the mortal body and its sanctification through the whole life fully describes the paradoxical character of Christ’s mystical incarnation in which Christ became a true human being like one of us without becoming a fallen sinner. I conclude that, according to Calvin, the vicarious humanity of Christ means that for the sake of our salvation Christ assumed a mortal body like ours and lived a perfect life in our miserable state. Therefore, Christ’s fallen humanity for us is the guarantee of reconciliation.
I concur with Ahn, and appreciate his insightful analysis on Calvin’s view of the vicarious humanity of Christ. Ahn would make a great Evangelical Calvinist; since the vicarious humanity of Christ is one of the touchstones of what it means to work within the mood of Evangelical Calvinism. It is this kind of Christ conditioned view of salvation that gets us into the trinitarian depth dimension of salvation that the classic forensic-juridical view of salvation simply cannot provide. Calvin is front and center for us, and shines brightest right here; that is when he emphasises the center of salvation in Christ.
The reality is, as Ahn develops in his essay, as Gregory of Nazianzus is oft quoted ‘the unredeemed is the unhealed’; and if Christ did not vicariously (participatorily-representatively) enter our fallen human state, then we are of all men most to be pitied. Alas, we remain in our sins, and we have no real hope or answer to our sin problem; which is a depraved heart toward God (who is salvation in his very life!). If Christ does not participate with us (fully), then we cannot participate with him fully in the divine plenitude of his shared life with the Father and Holy Spirit; in other words, we are not saved. This is why understanding and meditating on the vicarious humanity of Christ is so fundamental to the Christian’s life and spirituality; because it represents the very heart and deep caverns of the Gospel itself.
Original posted at another blog of mine: The Evangelical Calvinist In Plain Language
 Ho-Jin AhnSJT 65(2): 145–158 (2012) C Scottish Journal of Theology Ltd 2012 doi:10.1017/S0036930612000026, Ahn’s bio/contact: Korean Central Presbyterian Church of Queens, Bayside, NY 11364, USA firstname.lastname@example.org.