...the Father Almighty, maker of heaven and earth...and one only begotten Son Jesus Christ...and the Holy Spirit...
How can Christians claim to worship the ONE God, for God is ONE and there is no other, and yet at the same time, believe in the Trinity and say that this ONE God contains a three-ness? Official Orthodox catechetical terminology says: "One Divine Nature in three Persons" . I can accept this on faith and I truly believe the ineffable and incomprehensible God and be One God in three divine persons without being three gods. It is a mystery and it does defy understanding, as it should.
But from a lecture I heard recently, I offer this apologetic as a helpful explanation of the ONE who is beyond our understanding. An analogy:
I am myself. When I speak, my word is as much a part of me as myself, for it is I who have spoken and my word is inseparable from me. My word reveals who I am and shows my true character. I cannot speak without my breath, and my breath is as much a part of myself as myself, for without my breath I am not myself and I would cease to exist. And without my word I am not myself because self involves expression, and yet without myself neither my word can exist, nor my breath. Nor can my word exist without myself or my breath, and when I breathe my word comes from me. I am one.
Scripture teaches about the Word made flesh, Jesus the Annointed One (Christ, Messiah):
"In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things were made through Him, and without Him nothing was made that was made. In Him was life, and the life was the light of men. And the light shines in the darkness, and the darkness did not comprehend it." (John 1:1-5)
"And the Word became flesh and dwelt among us, and we beheld His glory, the glory as of the only begotten of the Father, full of grace and truth." John 1:14
"Jesus answered: "If I honor Myself, My honor is nothing. It is My Father who honors Me, of whom you say that He is your God. Yet you have not known Him, but I know Him. And if I say 'I do not know Him,' I shall be a liar like you: but I do know Him and keep His word. Your father Abraham rejoiced to see My day, and he saw it and was glad."
Then the Jews said to Him, "You are not yet fifty years old, and have You seen Abraham?"
Jesus said to them, "Most assuredly, I say to you, before Abraham was, I AM."
John 8: 54-58
And about the oneness of God, Jesus testifies:
"Do you not believe that I am in the Father, and the Father in Me? The words that I speak to you I do not speak on My own authority; but the Father who dwells in Me does the works. Believe me that I am in the Father and the Father in Me, or else believe Me for the sake of the works themselves." John 14:10-11
And about the Holy Spirit:
"And I will pray the Father, and He will give you another Helper, that He may abide with you forever-the Spirit of truth, whom the world cannot receive, because it neither sees Him nor knows Him; but you know Him, for He dwells with you and will be in you." John 14: 16-17
"But the Helper, the Holy Spirit, whom the Father will send in My name, He will teach you all things, and bring to your remembrance all things that I said to you." John 14:26
So, One God: the Father who begets the Word who became incarnate, Jesus Christ and who sends his Spirit, his breath, upon us in the name of His Word. Inseparably One God, mysteriously in three persons.