The Second person of the Trinity was not formed in Mary; but Christ was born of a woman

"The next heresy was that of Nestorius, who died sometime after A.D. 440. Even if the reports apply more to his disciples than to him, we know more about him than about other heretics because Cassian (360-432?) wrote sixty-nine pages of double columns (in the Post-Nicene Fathers) under the title The Seven Books of John Cassian on the Incarnation of the Lord, Against Nestorius. But though thus indebted to him, we cannot fully trust him, for, like the other Fathers, he uses too much invective. At the beginning of his treatise he describes Nestorius as a hydra, who hisses against us with deadly tongues. Book VI, Chapter vi starts with 'O you heretic . . . you wretched madman' and continues in VI, ix with 'What are you vomiting forth?' To which add, 'you wretched, insane, obstinate creature' (VI, xviii).
There is another and less dishonorable reason for reading Cassian and the other Fathers, with some suspicion. Unfortunately it applies to all authors. Even when modern scholars document their studies, it is always possible that they misunderstand some of their quotations. But this danger is greater when the subject matter is new, unfamiliar, and chaotic. The present writer will now select what he thinks are the most important of Cassian's references to Nestorius' theology. But the going is not smooth: Irrelevancies and fallacies beset us.
Nestorius, then, taught that Christ was born as a mere man (I, iii). A footnote at II, vi (p. 561, Nicene Fathers) reads, Nestorius maintained that 'that which was formed in the womb of Mary was not God himself.'' But this is no heresy. The Second Person of the Trinity was not formed in Mary. The Logos was never formed at all. He is eternal. Hence the argument against Nestorius, at this point, is a failure. Even the phrase from I,iii is unobjectionable, though perhaps too easily misunderstood. Christ was indeed born as mere men are, if this means from a woman's womb. But his conception was not that of an ordinary human baby. The trouble is that the language is loose, and Cassian too easily settles upon one interpretation. one should not be too surprised at this. When a group of men begin to discuss an utterly new subject, the terminology is bound to be imperfect." - Gordon H. Clark, Incarnation, Pg. 10-11