Here is the definition of the Trinity I have been utilizing: One God subsists in three persons, Father, Son, and Holy Spirit; co-equal and co-eternal. Recently, while talking with two Jehovah Witnesses I was challenged on my view of Jesus and the Father being co-equal.
All three persons are co-equal
They attacked equality of the Godhead by saying the Father was greater and had knowledge Jesus lacked. They used the verse in John 14:28 where Jesus says, “You heard that I said to you, ‘I go away, and I will come to you.’ If you loved Me, you would have rejoiced because I go to the Father, for the Father is greater than I.” I explained Jesus had two natures being fully God and fully man. In his human nature Jesus gave up the use of certain prerogatives such as all knowledge and subjected himself to the headship of the Father. In his divine nature He continued to have all the attributes of God. I said president Obama and I are equal in our human natures but since he is the president I could say he is greater than me. Jesus as a human could say the Father is greater, speaking about position, just like Obama is to me. Jesus and the Father are equal in they share the same divine nature. My Jehovah Witness friends struggled with the idea Jesus could be fully God and fully man. I took them to Philippians 2:5-8 “Have this attitude in yourselves which was also in Christ Jesus, 6 who, although He existed in the form of God, did not regard equality with God a thing to be grasped, 7 but emptied Himself, taking the form of a bond-servant, and being made in the likeness of men. 8 And being found in appearance as a man, He humbled Himself by becoming obedient to the point of death, even death on a cross.” I said as a human Jesus didn’t desire equality with the Father because he took on flesh (bond-servant) subjecting himself to death as a human something the Father cannot do. Philippians says he was in the “form of a bond-servant.” I asked do you believe Jesus was fully human? They said yes. I said the Greek word for form is “Morphe” which means nature or essence. Jesus had a human nature. Just like he had a human nature, we see in verse 6 Jesus also was in the form (morphe) of God. What that means is he also had the nature of God. Jesus was God taking on human flesh. As a human he didn’t use all his divine abilities. That’s what it means “…but emptied himself.” Jesus at times became tired, ate food, and died on a cross; all things only a human can do. On the cross the human Jesus died but the 2nd person of the Trinity, his divine nature, could never die.
They continued to challenge the equality issue by taking me to 1 Corinthians 11:2-3 “Now I praise you because you remember me in everything, and hold firmly to the traditions, just as I delivered them to you. 3 But I want you to understand that Christ is the head of every man, and the man is the head of a woman, and God is the head of Christ.” How can Jesus be equal if God the Father is the head over him? I said similar to a husband and wife being equal in their human natures, the Bible says the husband is to be head over his wife. The second person of the Trinity (Jesus) is equal in nature to the Father but takes a different role by taking on human flesh, and subjects himself to the headship of the Father. The Father and the Son can be co-equal, while at the same time the Son submits to the headship of the Father; similar to the headship of the husband over the wife.
The issue of equality depends on our understanding of how one God can subsist in three persons. I’ve had people ask, how can we say that God is one undivided being and yet in this one being there are three persons? First, we must understand that each person is fully God; that is each person has the fullness of God’s being in himself. The Son is not partly God or just one-third of God, but the Son is fully God. The Father and the Holy Spirit are each fully God. All three persons are co-equal. To help you understand how this works I have provided different circles to show the correct and incorrect ways to view the being of God.
If the Bible teaches the equality within the Trinity we should expect to see all three persons given equal status in the scriptures. This is clearly communicated by Matthew in his recording of what Jesus said as he commissioned his disciples. Matthew 28:19 “Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit.” Immediately, we notice Matthew says to baptize them in the name, singular. The conclusion is these three persons are the one God, thus we see the singular for “name.” In other places when listing multiple names, Matthew utilized “names” plural. In Matthew 10:2 “Now the names of the twelve apostles are these: The first, Simon, who is called Peter, and Andrew his brother; and James the son of Zebedee, and John his brother.” Matthew chose the singular Greek word for “name” because he was communicating the oneness and equality of one God subsisting in three persons. Even the Jehovah Witness Bible (NWT) uses name singular, while at the same time denying the Trinity.
The very names “Father” and “Son,” drawn as they are from the family, the most familiar of human institutions, indicate very strongly the distinct personhood of both the Father and the Son. When “the Holy Spirit” is put in the same expression and on the same level as the other two persons, it is hard to avoid the conclusion that the Holy Spirit is also viewed as a person and of equal standing with the Father and the Son. Matthew 28:19 provides strong support for the definition of the Trinity and the equality within the Godhead.
 Diagrams and descriptions based on Wayne Grudem’s work in Systematic Theology pgs. 253-255
 Grudem, Wayne, Systematic Theology, Zondervan Publ., 1994, p. 230