The following chart can be used to explain the Oneness of God in Christ Jesus according to what I was taught:
The circle on the left represents the one and only God, the Father. The circle on the right represents the Son, the man Jesus Christ. The man Jesus had a human body, human soul, and human spirit. Yet He was one in being with the Father. He is also the express image of the indwelling Father's own person. To see Him is to see the Father. To hear Him is to hear the Father. He is the human tabernacle of God Almighty.
The deepest, most unexplainable unity between the Father and the Son is in the "spirit". Christ's human spirit is "one" with the very Spirit of God. The natures are combined here. Thus the Holy Spirit is not only the "Spirit of God" (the Father) but is also the "Spirit of Christ" (the man Christ Jesus).
Jesus IS a man... yet He is ALSO God. Give Him Praise and Glory!
The Pharisees understood clearly what Jesus was claiming regarding His nature:
John 10:22-33 (ESV)
22 At that time the Feast of Dedication took place at Jerusalem. It was winter, 23 and Jesus was walking in the temple, in the colonnade of Solomon. 24 So the Jews gathered around him and said to him, “How long will you keep us in suspense? If you are the Christ, tell us plainly.” 25 Jesus answered them, “I told you, and you do not believe. The works that I do in my Father's name bear witness about me, 26 but you do not believe because you are not among my sheep. 27 My sheep hear my voice, and I know them, and they follow me. 28 I give them eternal life, and they will never perish, and no one will snatch them out of my hand. 29 My Father, who has given them to me, is greater than all, and no one is able to snatch them out of the Father's hand. 30 I and the Father are one.”
31 The Jews picked up stones again to stone him. 32 Jesus answered them, “I have shown you many good works from the Father; for which of them are you going to stone me?” 33 The Jews answered him, “It is not for a good work that we are going to stone you but for blasphemy, because you, being a man, make yourself God.”
They understood that Jesus, being a man, claimed to also be God by virtue of
oneness with the Father. Just as if I claimed to be absolutely one with God in spirit without measure, you'd laugh at me stating that I was just a man. But if I were truly "one" with God in a state of shared spiritual being... I'd also be God.
Jesus goes on to explain this "oneness" in greater theological detail when Phillip asks to see the Father in
John 14:
John 14:8-11
8 Philip said to him, “Lord, show us the Father, and it is enough for us.” 9 Jesus said to him, “Have I been with you so long, and you still do not know me, Philip? Whoever has seen me has seen the Father. How can you say, ‘Show us the Father’? 10 Do you not believe that I am in the Father and the Father is in me? The words that I say to you I do not speak on my own authority, but the Father who dwells in me does his works. 11 Believe me that I am in the Father and the Father is in me, or else believe on account of the works themselves.
The man Jesus Christ is also God.