02 Jul '13 12:22>1 edit
Through Christ’s work in His incarnation not only was God brought into man, but God was also made one with man. Christ has accomplished the great work of making God one with man, of making the two—God and man—one person with two natures, divinity and humanity. How this was accomplished we cannot explain. Nevertheless, the Bible reveals clearly that through Christ’s incarnation God in His divinity was made one with man in humanity. The two essences of divinity and humanity were made into a single entity without a third essence being produced. In this one entity the two essences of divinity and humanity are the original essences. Even after being mingled in the person of the God-man, they are distinct; there is no mixture. God is still God, and man is still man, yet they have become one person, Christ, the God-man, in whom God is one with man. No one can explain this adequately.
Christ was conceived of the Holy Spirit with the divine essence and born of a human virgin with a human essence. We use the word “essence” in a strong sense to denote something even more intrinsic than nature. The essence is the intrinsic constituent of a certain substance. Christ was conceived of the Holy Spirit not only with the divine nature but with the divine essence. Therefore, He has two essences, the divine and the human. These two essences were not merely added together; they were mingled together. In the conception of Christ the divine essence and the human essence were mingled.
It is crucial that we have the proper understanding of the word “mingle” with respect to Christ’s work of bringing God into man and of making God one with man through His incarnation. We definitely do not use this word to mean that the mingling of divinity with humanity in Christ caused a third nature to be produced, something that is neither divine nor human. To say that with respect to the Lord Jesus the mingling of the divine essence and the human essence produced a third nature, a nature that is neither fully human nor divine, is heretical. We agree with the first definition of mingle given in Webster’s unabridged dictionary: “to combine or join (one thing with another, or two or more things together), especially so that the original elements are distinguishable in the combination.” Hence, to mingle is to combine two or more things together so that the original elements remain distinguishable.
This certainly is the situation regarding Christ as the God-man. Because He was conceived of the divine essence and the human essence, He is the mingling of God and man. But both the divine essence and the human essence remain and are distinguishable. These essences are mingled in Him without producing a third nature. In His one person Christ possesses two essences, and in Him each essence is distinguishable. Therefore, it is altogether accurate to say that the incarnation of Christ was the mingling of God with man. This mingling produced a single person, a divine-human person, the person of the God-man. Although Christ has two essences, He does not have two persons.
The conception of the God-man was God’s incarnation, constituted not only by the divine power but also of the divine essence mingled with the human essence to produce the God-man. Through this great work accomplished by Christ, God was made one with man so that He might be manifested in the flesh (1 Tim. 3:16).
The Trinity is a great mystery. The incarnation is also a great mystery. All genuine Christians, all who hold to the common faith (Titus 1:4), must believe in the Triune God and in Christ’s incarnation. Christ is God made one with man. Although He has both divinity and humanity, He is not two persons. Christ is one person with two essences. Although we cannot explain this adequately, we can enjoy Him as the God-man. In incarnation Christ, the embodiment of the Triune God, accomplished the great work of bringing God into man and of making God one with man.
Further reading http://www.ministrybooks.org/books.cfm?id=229DC5
(my bolding above)