When it came to the Nicene Council, The Encyclopaedia Britannica states: “Constantine himself presided, actively guiding the discussions, and personally proposed . . . the crucial formula expressing the relation of Christ to God in the creed issued by the council . . . Overawed by the emperor, the bishops, with two exceptions only, signed the creed, many of them much against their inclination” (1971 edition, Vol. 6, “Constantine,” p. 386).
The ongoing disagreements were at times violent and bloody. Of the aftermath of the Council of Nicaea, noted historian Will Durant writes, “Probably more Christians were slaughtered by Christians in these two years (342-3) than by all the persecutions of Christians by pagans in the history of Rome” ( The Story of Civilization, Vol. 4: The Age of Faith, 1950, p. 8). Atrociously, while claiming to be Christian many believers fought and slaughtered one another over their differing views of God!
Notice this admission in the New Bible Dictionary, “The term trinity is not itself found in the Bible. It was first used by Tertullian at the close of the 2nd century, but received wide currency [common use in intellectual discussion] and formal elucidation [clarification] only in the 4th and 5th centuries.” — (1996, “Trinity”)
The New Bible Dictionary goes on to explain that “the formal doctrine of the Trinity was the result of several inadequate attempts to explain who and what the Christian God really is ... To deal with these problems the Church Fathers met in [A.D.] 325 at the Council of Nicaea to set out an orthodox biblical definition concerning the divine identity.” However, it wasn't until 381, “at the Council of Constantinople, [that] the divinity of the Spirit was affirmed.”
Wikipedia states what Tertullian believed on the Godhead:
Tertullian was just a forerunner of the Nicene doctrine and did not state the immanent trinity. His use of trinitas (Latin: 'Threeness') emphasised the manifold character of God. In his treatise against Praxeas he used the words, “Trinity and economy, persons and substance.” The Son is distinct from the Father, and the Spirit from both the Father and the Son. “These three are one substance, not one person; and it is said, 'I and my Father are one' in respect not of the singularity of number but the unity of the substance.” In his book Tertullian against Praxeas, he also states that the Son was not co-eternal with the Father and did have a beginning as the begotten Son of God. He also did not teach that the Holy Spirit was a literal being. So the trinity doctrine as we know it today did not even come from the man who introduced the word Trinity.
By no means are theologians' explanations of the trinity doctrine clear. Religious writer A.W. Tozer in his book The Knowledge of the Holy states that the trinity is an “incomprehensible mystery” and that attempts to understand it “must remain forever futile.” He admits that Churches, “without pretending to understand,” have nevertheless continued to teach this doctrine (1961, pp. 17, 18) He then remarkably concludes, “The fact that it cannot be satisfactorily explained, instead of being against it, is in its favor.” — (p. 23)
The New Unger's Bible Dictionary in its article on the trinity concedes that the Trinitarian concept is humanly incomprehensible, “It is admitted by all who thoughtfully deal with this subject that the Scripture revelation here leads us into the presence of a deep mystery; and that all human attempts at expression are of necessity imperfect.” — (1988, p. 1308)
Cyril Richardson, professor of Church history at New York's Union Theological Seminary, though a dedicated Trinitarian himself said this in his book The Doctrine of The Trinity, “My conclusion, then, about the doctrine of the Trinity is that it is an artificial construct ... It produces confusion rather than clarification; and while the problems with which it deals are real ones, the solutions it offers are not illuminating. It has posed for many Christians dark and mysterious statements, which are ultimately meaningless, because it does not sufficiently discriminate in its use of terms.” — (1958, pp. 148-149)
He also admitted, “Much of the defense of the Trinity as a 'revealed' doctrine, is really an evasion of the objections that can be brought against it.” — (p. 16)
A Dictionary of Religious Knowledge states regarding the trinity, “Precisely what that doctrine is, or rather precisely how it is to be explained, Trinitarians are not agreed among themselves.” — (Lyman Abbott, editor, 1885, “Trinitarians”)
These following admissions from a number of reputable sources and authors who, while themselves affirming the Trinity, acknowledge that the word Trinity and the doctrine is not found in the Bible.
The International Standard Bible Encyclopedia acknowledges that “'trinity' is a second-century term found nowhere in the Bible, and the Scriptures present no finished trinitarian statement.” — (1988, Vol. 4, “Trinity,” p. 914). It further states that “church fathers crystallized the doctrine in succeeding centuries”—long after the apostles had passed from the scene.
Martin Luther who was the German priest who initiated the Protestant Reformation said, “It is indeed true that the name 'Trinity' is nowhere to be found in the Holy Scriptures, but has been conceived and invented by man.” — (reproduced in The Sermons of Martin Luther, John Lenker, editor, Vol. 3, 1988, p. 406)
Historian and science fiction writer H.G. Wells in his noted work The Outline of History stated, “There is no evidence that the apostles of Jesus ever heard of the trinity—at any rate from him.” — (1920, Vol. 2, p. 499)
The HarperCollins Encyclopedia of Catholicism says, “Today, however, scholars generally agree that there is no doctrine of the Trinity as such in either the OT or the NT ... It would go far beyond the intention and thought-forms of the OT to suppose that a late-fourth-century or thirteenth-century Christian doctrine can be found there ... Likewise, the NT does not contain an explicit doctrine of the Trinity.” — (Richard McBrien, general editor, 1995, “God,” pp. 564, 565)
And the HarperCollins Bible Dictionary states, “The formal doctrine of the Trinity as it was defined by the great church councils of the fourth and fifth centuries is not to be found in the NT.” — (Paul Achtemeier, editor, 1996, “Trinity”)
Professor Charles Ryrie wrote, “Many doctrines are accepted by evangelicals as being clearly taught in the Scripture for which there are no proof texts. The doctrine of the Trinity furnishes the best example of this. It is fair to say that the Bible does not clearly teach the doctrine of the Trinity . . . In fact, there is not even one proof text, if by proof text we mean a verse or passage that 'clearly' states that there is one God who exists in three persons.” — (Basic Theology, p. 89)
He goes on to say, “The above illustrations prove the fallacy of concluding that if something is not proof texted in the Bible we cannot clearly teach the results . . . If that were so, I could never teach the doctrine of the Trinity.” — (lbid, p. 90)
Shirley Guthrie, professor of theology at Columbia Theological Seminary wrote, “The Bible does not teach the doctrine of the Trinity. Neither the word 'trinity' itself nor such language as 'one-in-three,' 'three-in-one,' one 'essence' (or 'substance'), and three 'persons,' is biblical language. The language of the doctrine is the language of the ancient church taken from classical Greek philosophy.” — (Christian Doctrine, 1994, pp. 76, 77)
Millard Erickson who is a research professor of theology at Southwestern Baptist Theological Seminary writes that the Trinity “is not clearly or explicitly taught anywhere in Scripture, yet it is widely regarded as a central doctrine, indispensable to the Christian faith. In this regard, it goes contrary to what is virtually an axiom of biblical doctrine, namely, that there is a direct correlation between the scriptural clarity of a doctrine and its cruciality to the faith and life of the church.
In view of the difficulty of the subject and the great amount of effort expended to maintain this doctrine, we may well ask ourselves what might justify all this trouble.” — (God in Three Persons: A Contemporary Interpretation of the Trinity, p. 12)
He further states that the Trinity teaching “is not present in biblical thought, but arose when biblical thought was pressed into this foreign mold [of Greek concepts]. Thus, the doctrine of the Trinity goes beyond and even distorts what the Bible says about God.” — (lbid, p. 20)
He also stated, “It is claimed that the doctrine of the Trinity is a very important, crucial, and even basic doctrine. If that is indeed the case, should it not be somewhere more clearly, directly, and explicitly stated in the Bible? If this is the doctrine that especially constitutes Christianity's uniqueness ... how can it be only implied in the biblical revelation? ... For here is a seemingly crucial matter where the Scriptures do not speak loudly and clearly.
Little direct response can be made to this charge. It is unlikely that any text of Scripture can be shown to teach the doctrine of the Trinity in a clear, direct, and unmistakable fashion.” — (lbid, pp. 108, 109)
Since the trinity is not found in the Bible as so many scholars and theologians admit, then how did it come to be viewed as such an important teaching? Theology professors Roger Olson and Christopher Hall explain part of the puzzle in their book The Trinity, “It is understandable that the importance placed on this doctrine is perplexing to many lay Christians and students. Nowhere is it clearly and unequivocally stated in Scripture ... How can it be so important if it is not explicitly stated in Scripture? ...
The doctrine of the Trinity developed gradually after the completion of the New Testament in the heat of controversy, but the church fathers who developed it believed they were simply exegeting [explaining] divine revelation and not at all speculating or inventing new ideas. The full-blown doctrine of the Trinity was spelled out in the fourth century at two great ecumenical (universal) councils: Nicea (325 A.D.) and Constantinople (381 A.D.).” — (2002, pp. 1, 2)