Jay Dyer says:
1) "[A consistent Calvinist must be] Nestorian, in that the Logos cannot assume a fallen human nature."
a) The Calvinist Position (whether right doctrine or error let Scripture decide)
Christ came in the likeness of sinful flesh (Romans 8:3). Christ, however, (and only Christ) was immaculately conceived. He was like the sinful flesh of Mary from whom he (after the flesh) came, but his flesh was not itself sinful. He was a true human, but he was the second Adam. He was not under Adam's federal headship and he did not inherit Adam's fallen and depraved nature. This is, of course, not only the Calvinist position but also the position of at least most of the major early church fathers who addressed the subject.
b) The Accusation Disputed
The Nestorian error is (to put it concisely) to deny the hypostatic union. Nestorianism, as it is classically defined, argues that Christ was not one person with two natures, but two persons. The existence of the hypostatic union is critical to the Calvinistic view of the atonement. The fact that the person of Christ was of infinite dignity on account of His divine nature makes the atonement of infinite intrinsic worth. The fact that the person of Christ had a truly human nature made the atoning death of Christ possible, as well as making the form of the sacrifice (death of man) a proper suffering of the penalty due. Without one or the other, the atonement would be impossible. Consequently, it would be impossible for a consistent Calvinist to embrace Nestorianism.
Furthermore, this alleged Nestorian error has been disputed. As A.A. Hodge explains in his Outlines of Theology:
The Nestorian heresy charged upon Nestorius, a Syrian by birth, and bishop of Constantinople, during the fifth century, by his enemy, Cyril, the arrogant bishop of Alexandria. Cyril obtained a judgment against Nestorius in the Council of Ephesus, A.D. 431, to the effect that he separated the two natures of Christ so far as to teach the coexistence in him of two distinct persons, a God and a man, intimately united. But it is now, however, judged most probable by Protestant historians that Nestorius was personally a brave defender of the true faith, and that the misrepresentations of his enemies were founded only upon his uncompromising opposition to the dangerous habit then prominently introduced of calling the Virgin Mary the mother of God because she was the mother of the human nature of Christ.
c) The Accusation Redirected
The Nestorians (those associated with the historical Nestorius) never went away, and (ironically) Rome now accepts the Nestorian communion under certain qualified circumstances (link), which (as the linked document cautions) should not be confused with the idea there is full communion between them.
On the other hand, Rome has proven Nestorius' apparent concerns over the term "theotokos" (literally "God-bearer" but often translated "mother of God") to be well founded. In the years since "theotokos" became accepted terminology, Mary grew to have an increasing role in the worship of Rome, until today we have apologists for Catholicism insisting that devotion to Mary is a mandatory part of religious life. Now, an official document from the Vatican from the 1970's states: "With his mind raised to heaven ... the priest should very often turn to Mary, the Mother of God, ... and daily ask her for the grace of conforming himself to her Son." (source) If Nestorius were still around today, he'd feel vindicated in opposing the term "theotokos" on the ground that it can lead to what amounts to Mary-worship (though modern Catholicism is careful not to call this sort of veneration of Mary "worship").
Continue to Part 3