Yet this raises another question. How did Christ not inevitably follow Adam? The Sunday school answer is, "He is God." True enough. But He is also fully human--yet without sin. And there's the catch. He became sin, yet without sin. Theologically (and philosophically) quite a bit of nuancing is necessary (and not just of the word "sin") in order to unpack this statement.
St Maximos begins by distinguishing between creaturely origin (geÃnesiß) on account of creation, and human birth (geÃnnhsiß) on account of Adam’s transgression. For St Maximos, the former corresponds to creation in the image of God (kat= eijkoÃna qeou`; Gen 1.27) while the latter corresponds to coming in the likeness of men (ejn oJmoiwÃmati ajnqrwÃpwn; Phil 2.7). According to His geÃnesiß, Christ took on human nature “in terms of the ‘vital inbreathing’ of man” (cf Gen 2.7) and therefore was a creature in the divine image. According to His geÃnnhsiß, Christ “voluntarily assumed the likeness of corruptible humanity” and therefore “willingly allowed himself to be made subject virtually to the same natural passions as us yet without sin.”
According to the axiom of St Gregory the Theologian (“what is not assumed is not healed, and what is united to God is saved”), the use of the word “virtually” is quite problematic. However, St Maximos does not mean that Christ nearly, or only in appearance, assumed human passions but that Christ assumed the “liability to passions” without assuming sinfulness. Using a careful juxtaposition, the Confessor explains what seems to be his understanding of the dual aspect in Christ's human nature.
[H]e is doubly identified by the two parts [in the human nature] of which he is constituted: he has perfectly become the New Adam, while bearing in himself the first
Adam, and he is both of these at once, without diminution. For, in being formed as a human being, he condescended to what was by law the creaturely origin [geÃnesiß] of Adamprior to his fall, and so assumed in his human nature impeccability through the divine “inbreathing,” but not incorruptibility. On the other hand, when, in his voluntary abasement, he underwent the human birth [geÃnnhsiß] punitively instituted after the fall, he assumed the natural liability to passions but not sinfulness. He became the New Adam by assuming a sinless creaturely origin [geÃnesiß] and yet submitting to a passible birth [geÃnnhsiß]. Perfectly combining the two parts in himself in a reciprocal relation, he effectively rectified the deficiency of the one with the extreme of the other, and vice versa, by causing his birth amid dishonor to save and renew his honorable creaturely origin and, conversely, by making his creaturely origin sustain and preserve his birth.