The Church Puts Its Foot Down
The matter was far from settled, despite Constantine’s high hopes. Arius and the new bishop of Alexandria, a man named Athanasius, began arguing over the matter even as the Nicene Creed was being signed; "Arianism" became a catchword from that time onward for anyone who did not hold to the Doctrine of the Trinity.
It was not until 451 CE, at the Council of Chalcedon that, the approval of the Pope, with the Nicene/Constantinople Creed was set as authoritative. Debate on the matter was no longer tolerated; to speak out against the Trinity was now considered blasphemy, and such earned stiff sentences that ranged from mutilation to death. Christians now turned on Christians, maiming and slaughtering thousands because of a difference of opinion.
Brutal punishments and even death did not stop the controversy over the Doctrine of the Trinity, and it continues even today.
The majority of Christians, when asked to explain this fundamental doctrine of their faith, can offer nothing more than: "I believe it because I was told to do so." It is explained away as "mystery" -- yet the Bible says in I Corinthians 14:33 that: "... God is not the author of confusion..."
The Unitarian denomination of Christianity has kept alive the teachings of Arius in saying that God is One; they do not believe in the Trinity. As a result, mainstream Christians abhor them, and the National Council of Churches has refused their admittance. In Unitarianism, the hope is kept alive that Christians will someday return to the preachings of Jesus: "...Thou shalt worship the Lord thy God, and Him only shalt thou serve." [Luke 4:8]
Islam and the Matter of the Trinity
While Christianity may have a problem defining the essence of God, such is not the case in Islam.
The Quran says (what means):
"They have certainly disbelieved who say: ‘Allah is the third of three’. And there is no god except One God." [Quran 5:73]
Suzanne Haneef, in her book, What Everyone Should Know About Islam and Muslims, (Library of Islam, 1985), puts the matter rather concisely when she says: "But God is not like a pie or an apple which can be divided into three thirds which form one whole; if God is three persons or possesses three parts, He is assuredly not the Single, Unique, Indivisible Being which God is and which Christianity professes to believe in." (pp. 183-184)
Looking at it from another angle, the Trinity designates God as being three separate entities -- the Father, the Son and the Holy Spirit. If God is the Father and also the Son, He would then be the Father of Himself because He is His own Son. This defies logic.
Christianity claims to be a monotheistic religion. Monotheism, however, has a fundamental belief that God is One; the Christian doctrine of the Trinity -- God being Three-in-One -- is seen by Islam as a form of polytheism. Thus, Christians do not worship just One God, they worship three.
This is a charge not taken lightly by Christians, however. They, in turn, accuse the Muslims of not even knowing what the Trinity is, pointing out that the Quran sets it up as Allah the Father, Jesus the Son, and Mary his mother. While veneration of Mary has been an invention of the Catholic Church since 431 CE, when she was given the title "Mother of God" by the Council of Ephesus, a closer examination of the verse in the Quran (5:116) most often cited by Christians in support of their accusation, shows that the designation of Mary by the Quran as a "member" of the Trinity, is simply not true.
While the Quran does condemn both trinitarianism (Quran 4:17) and the worship of Jesus and his mother Mary (Quran 5:116), nowhere does it identify the actual three components of the Christian Trinity. The position of the Quran is that who or what comprises this doctrine is not important; what is important is that the very notion of a Trinity is an affront against the concept of One God.
In conclusion, we see that the Doctrine of the Trinity is a concept conceived entirely by man; there is no sanction whatsoever from God to be found regarding the matter, simply because the whole idea of a Trinity of divine beings has no place in monotheism. In the Quran -- God's Final Revelation to humankind -- we find His stand quite clearly stated in a number of eloquent passages (which mean): "Say: ‘I am only a man like you, to whom has been revealed that your god is One God. So whoever would hope for meeting with his Lord – let him do righteous work and not associate in the worship of his Lord anyone.’” [Quran 18:110]
And (which means):
"...And do not make (as equal) with Allah another deity, lest you be thrown into Hell, blamed and banished." [Quran 17:39]
Allah tells us over and over again in a Message that is echoed throughout all His Revealed Scriptures (what means):
"...and I am your Lord, worship Me ..." [Quran 21:92]