باسمك اللهم
Let me get right to the point: an early Church father and Christian theologian, Tertullian (d.220 CE), a staunch advocate of the Trinity doctrine, confessed in his writings that the majority of Christians in his time, whom he refers to as “Believers” not only rejected the Trinity, but held it in contempt as nothing more than thinly veiled tritheism: “The simple, indeed, (I will not call them unwise and unlearned) who always constitute the majority of believers, are startled at the dispensation (of the Three in One), on the ground that their very rule of faith withdraws them from the world's plurality of gods to the one only true God; not understanding that, although He is the one only God, He must yet be believed in with His own dispensation. The numerical order and distribution of the Trinity they assume to be a division of the Unity; whereas the Unity which derives the Trinity out of its own self is so far from being destroyed, that it is actually supported by it. They are constantly throwing out against us that we are preachers of two gods and three gods, while they take to themselves preeminently the credit of being worshipers of the One God; just as if the Unity itself with irrational deductions did not produce heresy, and the Trinity rationally considered constitute the truth. We, say they, maintain the Monarchy (or, sole government of God)
Source: Against Praxeas; ch. III
Based on this quote, I have some questions for trinitarian Christians:
1. Are those Christians who reject the Trinity still considered ‘Believers’? Tertullian apparently thought so
2. If the answer to the first question is yes, does that not indicate that belief in the Trinity is not a necessary doctrine for faith?
3. If the Trinity is so evident from Scripture and the teachings of the Apostles, why, according to Tertullian, was it rejected by the majority of Christians as late as the 3rd century CE?
In fact, if you study the development of this Trinity doctrine, you will see that the earliest mention of the word Trinity in Christian literature is in the late 2nd century CE by the theologian Theophilus of Antioch (d. 183 CE). But curiously, he defines the Trinity contrary to the so-called orthodox conception of ‘Father, Son, Holy Spirit’, instead claiming that the Trinity is “God, His Word [Logos], and His Wisdom [Sophia]”
Source: Apology to Autolycus
In summary, it is quite apparent to me the Trinity doctrine was developed by certain theologians and then made an essential part of the Christian dogma by powerful Bishops. It was certainly not taught by Jesus of Nazareth or his disciples and apostles. It is certainly not taught in the Hebrew Bible, which zealously affirms unitarian monotheism.