Explain the main differences between ontological and functional Christologies as they relate to the person and work of Christ. In your estimation, what is the value of considering both of these approaches to Christology as two sides of the same coin?
Functional and ontological Christology, although different relate in countless ways. While ontological Christology deals with the relationship of Christ to the Father, the functional deals with Jesus Christ’s unique function or role as a member of the Trinity. Both of these categories are essential to our doctrine. This is also the common theme throughout our text when Mr. Horton states, “the sonship-as-office is as important as his ontological sonship as the eternal Word.” It is hard to bring up one topic without the other being discussed. As a body of Christ, we have more in common regarding what we all believe was Jesus’ function, but less commonality as it refers to the ontological relationship of Christ to the Trinity. This is where many heresies and false doctrines are born. It is also the origin of cults and ministries that violate the essential first-order doctrines of faith.
The functional branch of Christology addresses the role and job of Jesus Christ, specifically His role as Savior and Messiah. Christ’s purpose of being here on earth was to come “fulfill the Law”. There had to be a living sacrifice sufficient enough to be shed for all mankind. Jesus was the only answer to that problem. Another function would be His example of life here on earth set through His physical ministry. As we know from Scripture, Jesus lived a perfect and blameless life of ministry to others, fulfilling His destiny in several different ways. By living and serving without sin, he was simultaneously also fulfilling His role as Savior. I would like to point out that it is amazing that Jesus did all of this so seamlessly without sin, not by sitting at home on the couch avoiding trouble in hopes to remain blameless, but by engaging the problems of the world head on.
The ontological branch of Christology deals with the identity of Christ as His relationship to the Father. It is in this field where questions are addressed such as, “who is He?” and “What is His relationship to God?” God’s Word tells us that He is God’s only begotten Son who came to save the world from their sins (John 3:16). Jesus also states Himself that He is equal with God the Father (John 10:30, 8:58). God the Father confirms these things when Jesus was baptized (Matthew 3:17; Rev. 1 & 2; John 1:1-3). These are just a few of the topics that are addressed in ontological Christology. As far as their value and association, both of these Christological topics are essential to our faith. They also both come as a package deal. Christ simply cannot be one without the other. If He did not fulfill his function and duty, He must have certainly not been able to claim His ontological connection to God the Father. This is why Apologists make the claim that Jesus is either who He says He is, or He is a bold-faced liar. I choose to believe the evidence that Jesus Christ is my Lord and Savior, Son of God, and one with my Father in paradise.
 Horton, Michael. 2011. The Christian Faith: A Systematic Theology for Pilgrims on the Way. Grand Rapids, MI: Zondervan. GCU database. 463