You, of course, are correct. The Universal Church was not formally organized until 325 A.D. at Nicea. The doctrine of the Trinity was accepted as dogma by this new Imperial State Religion. Later at Constantinople (381 A.D.) the doctrine was made official and complete. In addition to this apostasy the Church began to kill folks in the name of God....those who would not convert or accept this new Trinity Theory.
At the same time other non biblical practices began to emerge from this State Religion such as Mary worship, Penitence, Transubstantiation, Indulgences, Infant Baptism from Jesus' name to the titles Father, Son and Holy Ghost.
The power of this State religion knew no bounds and grew to be the biggest, richest and most influential political movement in the world. Many Churches eventually broke away because of these practices....but yet, kept the false doctrine of the Trinity without questioning it.
So, where did this doctrine come from? It began in Babylon where much apostasy had it's start [Revelation 17:3-5]. It then spread throughout the ancient world. Babylon's Triad was "Nimrod/Father, Tammuz/Son, and Semirimus/Mother". The Triad of Egypt was called "Osiris, Horus, and Isis"; Greece..."Zeus, Apollo and Athena"; India..."Brahma, Vishnu and Shiva"; Rome..."Jupiter, Mars and Venus"; Catholicism..."Father, Son and Holy Ghost".
The Trinity of back slided Israel was called Baal/Father, Tammuz/Son and Ashtoreth/Mother.....and yes, it too came from Babylon.
After the Israelites of the north had been taken captive to Assyria (721 B.C.) for worshiping these same Babylonian Gods the king of Assyria repopulated the north with folks from Babylon....and they became known as Samaritans. [II Kings 17:6] In the ninth year of Hoshea, the king of Assyria captured Samaria and deported the Israelites to Assyria. He settled them in Halah, in Gozan on the Habor River and in the towns of the Medes. (verse 7) All this took place because the Israelites had sinned against the LORD their God, who had brought them up out of Egypt from under the power of Pharaoh king of Egypt. They worshiped other gods.
[II Kings 17:24] The king of Assyria brought people from Babylon, Cuthah, Avva, Hamath and Sepharvaim and settled them in the towns of Samaria to replace the Israelites. They took over Samaria and lived in its towns. (verse 33) They worshiped the LORD, but they also served their own gods in accordance with the customs of the nations from which they had been brought. To this day they persist in their former practices. They neither worship the LORD nor adhere to the decrees and ordinances, the laws and commands that the LORD gave the descendants of Jacob, whom he named Israel.
These folks....the Samaritans of Babylonian extraction, were the same people our Lord cautioned the Apostles about when he said: [Matthew 10:5-6] These twelve Jesus sent out with the following instructions: "Do not go among the Gentiles or enter any town of the Samaritans. Go rather to the lost sheep of Israel."
Simon Magus was a Samaritan....a descendant of Babylonians and we read in [Acts 8:9-11]Now for some time a man named Simon had practiced sorcery in the city and amazed all the people of Samaria. He boasted that he was someone great, and all the people, both high and low, gave him their attention and exclaimed, "This man is the divine power known as the Great Power." They followed him because he had amazed them for a long time with his magic."
Simon was a Trinitarian because he still believed in the religion of his Fathers [II Kings 17:33-34] Simon is mentioned quite frequently by the Church Fathers as being in Rome....supposedly at the same time Peter was to have been there....although this has always been impossible to square with scripture. Simon, after his rejection by Peter, began to fashion his own "Christian" church -- a church of which HE was head -- a church designed to completely overthrow the True Church of God. His idea was to blend together Babylonian teaching with some of the teachings of Christ -- especially to take the name of Christ -- and thus create one universal church! But a church with Babylonianism as its basis. Luke gives in detail the principal character who established the so called Christian counterpart of the Truth in the Apostles’ days. This is the reason the Apostles in their Church letters many times mention the false system as already in existence, but fail to describe its origin. They didn't have to. That was already done right in chapter 8 of Acts....by Luke!
So....Tertullian may have "coined" the word Trinity....but the concept had been around for some time.
[Acts 2:38]Peter replied, "Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit.
But --- if the Father, the Son, and the Spirit of God were the "us" who created the world and everything in it, then all of these Triads are counterfeits of the real Trinity of Scripture. The Father, Son, and Holy Spirit existed long before these pagan Triads who were just imitations of what the deceiving spirits knew the truth to be.
Pagans also prayed to their god[s] --- does that make prayer a pagan practice? Pagans sacrificed to their god[s]? Did that make Israel's sacrifices pagan practices? There were a lot of things that the pagans did that the Jews and the Christians also did. But the big question is: "who was imitating whom?"
Furthermore, the Babylonians, the Greeks, the Persians, the Egyptians, the Greeks, the Romans, ... all worshipped a lot more than just a three god Triad. The emergence of a Triad from all of these gods that they worshipped would very well be an acknowledgment from deep within them, or the deceiving spirits guiding them, that the real God is a Trinity. Their Triad would be their attempt at a counterfeit Godhead --- an imitation of the truth not vice versa.
Please explain to me who these three are: the Father, Jesus, and the Holy Spirit. Are they all the same person? If so where does it say so in the New Testament?
The only person in the early church that I am aware of that ever claimed to be the Father-the Son-and the Holy Spirit, all in one person, was none other than the great sorcerer SIMON MAGUS himself. He wasn't a Trinitarian. He was a UNITARIAN.