From the Orthodox Study Bible:

The center of Christianity is the Lord Jesus Christ Himself. In fact, He is the centerpiece of all history. But the world struggles with His identity. Who is He? Is He God? Is He man? Both? The Scriptures clearly answer these crucial questions.

In his Gospel, John gives a specific and definitive explanation of who Christ is. “In the beginning was the Word, and the Word was with God, and the Word was God” (1:1). John the Baptist, the forerunner of Christ, revealed God the Word as “the

"...Truly, this was the Son of God."*

“…Truly, this was the Son of God.”*

  1. He is God, for He was with God from before all time. Clearly, the One born Jesus of Nazareth did not have His beginning in His earthly birth. Rather, He is the eternal Son of God, without beginning. There never was a time when the Son of God did not exist.
  2. He is also man, for He “became flesh.” He has become one of us, being like us in all things but without sin.
  3. He acts both as God and as man, doing what is appropriate for each nature in the unity provided by His one divine Person. Never does divine nature and activity become changed into human nature and activity. The two are in union without confusion. Christ does, however, “energize” human nature with divine energy so that human nature is redeemed from sin and death and brought into union with God. He thus “deifies” humanity.

The miracle of these incomparable truths is known as the knowledge of Christ, or “Christology.” Many documents have expounded on Christology, but the definitive text is the Nicene Creed, the outcome of the first and second Ecumenical Councils in the fourth century. The Creed of Chalcedon (issued by the fourth Ecumenical Council, A.D. 451) embodies other truths concerning the Incarnation of the Word. These creeds set the doctrinal fences outside of which we do not wander in our knowledge of Christ.

The Apostle John bears witness to Christ: “That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked upon, and our hands have handled, concerning the Word of life-the life was manifested, and we have seen, and bear witness, and declare to you that eternal life which was with the Father and was manifested to us-that which we have seen and heard we declare to you, that you also may have fellowship with us; and truly our fellowship is with the Father and with His Son Jesus Christ” (1 John 1:1-3).

We, too, bear witness to Jesus Christ. For since God became man, and we are united with Him in baptism, we experience His Incarnation in our lives. The miracle of Christology for us is that, as the Son of God became man, we in turn may partake of God.

*The icon of Martyr Longinus the Centurion was found here.