Nestorius had argued that Jesus Christ had two persons and two natures. The decision at the council of Ephesus in AD 431 was that Jesus Christ could not be considered as consisting of two persons, one man and the other God, and that he did not have two separate natures, one human and one divine. Mor Koorilose explains it as ‘one nature of the incarnate word’.
Eutyches taught that human nature merges into the divine nature to become one nature. Our Church has not accepted this.
According to the Tome of Leo the human and divine natures of Jesus Christ are separate and all his activities can be divided into human and divine. This theory was completely against the convictions of the council of Ephesus of 431 A.D. So the churches of Antioch and Alexandria did not agree to the decisions of the Chalcedon council.
Regarding Christology, the four oriental churches including the Syrian Orthodox Church follow the faith declared at the Ephesus council of 431 A.D.
Human nature does not become divine nature and divine nature does not become human. The human and divine natures neither become a mixture nor merge and become one. One nature does not destroy the other. Instead divine nature in completeness and human nature in completeness except for sin are inseparable in one essence.
The Churches that did not accept the dyophysite theory are known as the Oriental Orthodox Churches today. Syrian orthodox, Coptic orthodox, Armenian orthodox and Abyssinian orthodox (Ethiopian) churches belong to this group