John S Romanides on Chalcedonian vs non - Chalcedonian .

" 1) Nestorius rejected the fact that He Who was born of the Virgin is consubstantial with the Father according to divinity and thus by nature God. Another way of saying this is that he rejected the fact that He Who before the ages is born from and is consubstantial with the Father was in the last days born according to His Own and proper humanity from the Virgin Mary having become thus by nature man and consubstantial with us. On the basis of this rejection Nestorius distorted the true significance of the title Theotokos which he in reality denied to the Mother of God. The most Nestorius could say is that Christ is the one person of the union of two natures, the one nature being by nature God and the other by nature man. The name Christ is not properly predicated of the Logos, but is the narne of the person of union born of Mary and in whom the Logos dwells and who was assumed by the Logos. Nestorius fanatically insisted that the Logos was not born of the Virgin according to His Humanity and did not, therefore, become by nature man. On the basis of this he divided the natures and predicates of Christ attributing the human to the assumed man and the divine to the Logos.

      In the light of his denial of the two births of the Logos and the double consubstantiality of the One and the Same Logos, Son of God and the Self-Same also Son of Mary, and thus of the true meaning of the title Theotokos, Nestorius insistence that he does not divide Christ into two persons, but only the natures and names, was judged a mockery of the faith and on this basis he was condemned by the Third and Fourth Ecumenical Councils and rejected by john of Antioch and Leo of Rome. ". ( from http://www.romanity.org ) Copyright John.S Romanides