Although Trinity is the most important doctrine within most of Christendom's 41,000 denominations, Trinitarians ignore the following facts:
1. There are no scriptures in the Judeo-Christian Bible in support of the dogma of a 3-in-1 god, in which there are three persons (Father, Son, and Holy Ghost) that are co-equal and co-eternal.
You start off with an incorrect premise. There are MANY Scriptures that state explicitly that Jesus is God.
Question: In Genesis 1, who created everything that was Created?
Answer: God.
Question: In John 1:1-3, who created everything that was Created?
Answer: The Word (Logos), which was God, and was WITH God (meaning there were more than one being that is God).
Question: What happened to the Word that was God and was with God?
Answer: According to John 1:14, the Word became flesh and we know it as the man Jesus.
Question: What does that mean about the man Jesus?
Answer: The man Jesus is God, since He is the embodiment of the Word of God.
2. Neither Jesus Christ nor his disciples of the 1st century AD promoted the teaching that there are three persons within a godhead, all of whom are co-equal and co-eternal.
Again, this is incorrect. Jesus claimed to be God on several occasions, (John 8:58, John 10:30, John 5:18). And His Apostles claimed He was God (John 20:28, 2 Pet 1:1, Tit 2:13, Heb 1:8).
3. Trinity did not become official Christian teaching until the 4th century AD, some 300 years after Jesus Christ left the earthly scene and returned to heavenly life, and some 300 years after the last book of the Bible was written.
The last book written by one of the Apostles that we have in common acceptance as Scripture today was written almost 60 years after Jesus' death. So either subtract 60 from the first 300, or add 60 to your second 300. (nitpicking, yes, but I am seeking accuracy because you are trying to make it seem that Scripture is not accurate in what it says).
To your point though, a doctrinal statement doesn't have to be made until and unless someone is attacking the foundation of an understanding that already exists. There was no need to defend the doctrine of Jesus being God until the attack on Jesus' deity became widespread. The Apostles knew He was God, taught that He was God to the first several generations of Christ followers, and it was not until 300 years later that an all out attack on His deity became prevalent.
It would surprise some that there were trinity gods throughout the pagan world--for centuries before the idea of a 3-in-1 god was adopted by Christendom. Below are four such examples:
A. In the 2nd century BCE (two centuries before Jesus Christ came to the earth), Egypt had a triad of gods consisting of (1) Horus, (2) Osiris, and (3) Isis.
B. In the 2nd century B.C.E., Babylon had a triad of gods consisting of (1) Ishtar, (2) Sin, and (3) Shamash.
C. In the 1st century C.E., Palmyra, which was an ancient city in Syria, had a triune god which consisted of (1) moon god, (2) Lord of Heavens, and (3) sun god.
D. Even the Hindus in India have their own trinity of gods, as follows: (1) Brahma, (2) Vishnu, and (3) Shiva.
Let's look at these religions. Not a single one of them portrays their deity as reaching out to His creation in order to reestablish the relationship broken because of sin. ONLY the true God of the universe did that. Further, all of those are worshiped as three separate deities. The Father, Son, and Holy Spirit are not three deities, but are ONE God.
QUESTIONS FOR DISCUSSION:
1. If the teaching of a Trinity god is essential to Christianity, how is it that the doctrine is nowhere to be found in scriptures within Jehovah's inspired word, the Judeo-Christian Bible?
The doctrine of the trinity of God is all over in Scripture. All the way back in the beginning of the Bible, Gen 1 depicts God talking to Himself as "Our", "Us", etc.
2. If Jesus Christ is part of a trinity in which he has the same power (co-equal) and the same eternity (co-eternal) as Jehovah the Father, how is it that the scriptures repeatedly inform us that Jesus Christ is subservient to Almighty God Jehovah (indicating inequality) and why is it that scripture tells us over and over again that Jesus Christ is "begotten" (indicating he had a beginning)?
Jesus as a man was subservient to the Father, because He emptied Himself of His glory, independent use of His power, position, etc. (Phil 2:7) when He came down from Heaven to become a man. As a man, He was subject to every weakness we as humans are subject to: sickness, hunger, fear, disappointment, longing, surprise, death, thirst, etc. But the Spirit within Him was not a human spirit (the spirit like you and I have), but was the Spirit of Almighty God. And that Spirit did not have a beginning, but was from eternity, and was responsible for creating all that has been created.
That Spirit could not have created itself, so it cannot be a created being.
