In order to understand the influence of paganism on the doctrine of the Trinity, we need to first understand the world into which Christianity was born and developed. The disciples, the first believers in Jesus, were Jews. In fact Christianity started out as a movement within Judaism. Like Jews since the time of Moses, these first believers kept the Sabbath, were circumcised and worshiped in the Temple: “One day Peter and John were going up to the temple at the time of prayer—at three in the afternoon.” [Acts 3:1] The only thing that distinguished the early followers of Jesus from any other Jews was their belief in Jesus as the Messiah, that is, the one chosen by God who would redeem the Jewish people. Today, many Christian scholars agree that authors of the New Testament such as Matthew were Jewish believers in Jesus. The influence of Judaism on the New Testament is important because it helps us to correctly understand its message. The New Testament is full of terminology like “son of God.” Such language is interpreted literally by Trinitarians to mean that Jesus is God the Son, but is this correct? What was the intention behind the Jewish writers of the New Testament when they used such language? What did these terms mean at the time of Jesus?
THE LANGUAGE OF THE BIBLE
When we turn to the Old Testament we find that such language permeates its pages. For example, Moses calls God “Father”: Is this the way you repay the Lord, you foolish and unwise people? Is he not your Father, your Creator, who made you and formed you? [Deuteronomy 32:6] Angels are referred to as “sons of God”: Now there was a day when the sons of God came to present themselves before the Lord, and Satan came also among them. [Job 1:6] The Old Testament even goes so far as to call Moses a god: “And the LORD said unto Moses, See, I have made thee a god to Pharaoh: and Aaron thy brother shall be thy prophet.” [Exodus 7:1] The Israelites are also referred to as “gods”: “I said, ‘You are “gods”; you are all sons of the Most High.’” [Psalm 82:6] What we can conclude is that such highly exalted language was commonplace and is intended figuratively; it is not a literal indication of divinity.
Even as late as the end of the first century, when the New Testament writers started penning their accounts of the life of Jesus, Jewish people were still using such language figuratively. In a conversation between Jesus and some Jewish teachers of the law, they say to Jesus: “…The only Father we have is God himself.” [John 8:41] The Gospel of Luke calls Adam a son of God when it recounts the lineage of Jesus: “the son of Enosh, the son of Seth, the son of Adam, the son of God.” [Luke 3:38] Jesus even says that anyone who is makes peace is a child of God: “Blessed are the peacemakers, for they will be called children of God.” [Matthew 5:9] If the New Testament writers understood such language to be a claim to divinity, then they would have used it exclusively in relation to Jesus. Clearly, it denotes a person that is righteous before God and nothing more.
So we can see that such language, in and of itself, does not denote the divinity of Jesus. So where did such ideas come from?
THE MINDSET OF THE PEOPLE WHO RECEIVED THE GOSPEL MESSAGE
The turning point in history came when Christianity ceased being a small movement within Judaism and Gentiles (non-Jews) started to embrace the faith in large numbers. We need to look to the pagan world of the Gentiles in order to understand the mindset of the people that received the New Testament message. Since the time of Alexander the Great, Gentiles had been living in a Hellenistic (Greek) world. Their lands were dominated by Roman armies, with the Roman Empire being the superpower of the world at the time. The Roman Empire itself was heavily influenced by Hellenistic religion, philosophy and culture. Greek gods and goddesses like Zeus, Hermes and Aphrodite, as well as Roman gods and goddesses like Jupiter, Venus and Diana, dominated the landscape. There were temples, priesthoods, and feasts dedicated to the patron god or goddess of a city or region; statues to the deities dotted the forums of the cities. Even rulers themselves were frequently worshipped as gods.
Gentiles from such a polytheistic background would have naturally understood Christian preaching about the “son of God” in light of a Greek or Roman god having been begotten by another. We can see this mindset manifested in the New Testament. In the Book of Acts there is an incident where the Gentile crowds think that Paul is Zeus come among them when he heals a crippled man:
When the crowd saw what Paul had done, they shouted in the Lycaonian language, “The gods have come down to us in human form!”
Barnabas they called Zeus, and Paul they called Hermes because he was the chief speaker.
The priest of Zeus, whose temple was just outside the city, brought bulls and wreaths to the city gates because he and the crowd wanted to offer sacrifices to them. [Acts 14:11-13]
It is worthy of note that Paul and Barnabas did not take this opportunity to explain that it was not they but rather Jesus who was God come in human form. Such a clarification is what you would expect, if Trinitarian beliefs about Jesus are correct. Instead, they argued against such pagan beliefs and practices:
But when the apostles Barnabas and Paul heard of this, they tore their clothes and rushed out into the crowd, shouting:
“Men, why are you doing this? We too are only men, human like you. We are bringing you good news, telling you to turn from these worthless things to the living God, who made heaven and earth and sea and everything in them. [Acts 14:14-15]
Here we see that the Greco-Roman peoples that Paul and Barnabas were preaching to were in the habit of taking humans for gods. Despite Paul protesting that he was not a god, the people persisted in their belief: “Even with these words, they had difficulty keeping the crowd from sacrificing to them.” [Acts 14:18] From this example we can see that according to Christian history, it was a common practice for people to attribute divinity to other humans. In spite of Paul openly denying being a god, the people continued to worship and sacrifice to him. We can conclude that even if Jesus himself rejected being God at that time, the mindset of the people was such that they would still have found a way to deify him. This is not an isolated incident, as we read elsewhere that Gentiles believed Paul was a god because he survived a bite from a venomous snake:
Once safely on shore, we found out that the island was called Malta.
The islanders showed us unusual kindness. They built a fire and welcomed us all because it was raining and cold.
Paul gathered a pile of brushwood and, as he put it on the fire, a viper, driven out by the heat, fastened itself on his hand.
When the islanders saw the snake hanging from his hand, they said to each other, “This man must be a murderer; for though he escaped from the sea, the goddess Justice has not allowed him to live.”
But Paul shook the snake off into the fire and suffered no ill effects.
The people expected him to swell up or suddenly fall dead; but after waiting a long time and seeing nothing unusual happen to him, they changed their minds and said he was a god. [Acts:28:1-6]
With this background in mind, it’s easy to see how Judaic phrases like “son of God” took on a different meaning when transported out of their Jewish monotheistic context into pagan Greco-Roman thought. The Trinity doctrine arose neither in a vacuum, nor strictly from the text of Scripture. It was the result of the influence of certain beliefs and attitudes that prevailed in and around the Church after the first century. The Church emerged in a Jewish and Greek world and so the primitive Church had to reconcile the notions they had inherited from Judaism with those they had derived from pagan mythology. In the words of the historian and Anglican bishop John Wand, “Jew and Greek had to meet in Christ” 
LINKS TO THE PAGANISM OF OLD
It’s interesting to note that the Greco-Roman religions were filled with tales of gods procreating with human beings and begetting god-men. The belief that God could be incarnate, or that there were sons of God, were common and popular beliefs. For example, the chief god in the Greek pantheon, Zeus, visited the human woman Danae in the form of golden rain and fathered Perseus, a “god-man.” In another tale Zeus is said to have come to the human woman Alcmena, disguised as her husband. Alcmena bore Hercules, another “god-man.” Such tales bear a striking similarity to Trinitarian beliefs of God being begotten as a man. In fact, the early Christian apologist Justin Martyr, considered a saint in the Catholic Church, said the following in response to pagan criticisms that Christianity borrowed from their beliefs about the sons of God:
When we say that the Word, who is our teacher, Jesus Christ the first born of God, was produced without sexual union, and that he was crucified and died and rose again, and ascended to heaven, we propound nothing new or different from what you [pagans] believe regarding those whom you consider sons of Jupiter. 
According to ancient Roman myth, Jupiter was the king of all the gods. Here Justin Martyr is telling Roman pagans that what the Christians believe about Jesus being the son of God is nothing different than what they believe about the sons of the god Jupiter. That the Church Fathers’ conception of the Trinity was a combination of Jewish monotheism and pagan polytheism can be seen in the testimony of Gregory of Nyssa, a fourth century bishop who is venerated as a saint in the Roman Catholic and Eastern Orthodox Churches. He also happens to be one of the great figures in the history of the philosophical formulation of the doctrine of the Trinity. He wrote:
For the truth passes in the mean between these two conceptions, destroying each heresy, and yet, accepting what is useful to it from each. The Jewish dogma is destroyed by the acceptance of the Word and by belief in the Spirit, while the polytheistic error of the Greek school is made to vanish by the unity of the nature abrogating this imagination of plurality. 
The Christian conception of God, argues Gregory of Nyssa, is neither purely the polytheism of the Greeks nor purely the monotheism of the Jews, but rather a combination of both.
Even the concept of God-men who were saviours of mankind was by no means exclusive to Jesus. Long before Jesus was born, it was not uncommon for military men and political rulers to be talked about as divine beings. More than that, they were even treated as divine beings: given temples, with priests, who would perform sacrifices in their honour, in the presence of statues of them. In Athens for example, Demetrios Poliorcetes (Demetrios the Conqueror of Cities, 337–283 BCE) was acclaimed as a divine being by hymn-writers because he liberated them from their Macedonian enemies:
How the greatest and dearest of the gods are present in our city! For the circumstances have brought together Demeter and Demetrios; she comes to celebrate the solemn mysteries of the Kore, while he is here full of joy, as befits the god, fair and laughing. His appearance is solemn, his friends all around him and he in their midst, as though they were stars and he the sun. Hail boy of the most powerful god Poseidon and Aphrodite! For other gods are either far away, or they do not have ears, or they do not exist, or do not take any notice of us, but you we can see present here, not made of wood or stone, but real. So we pray to you: first make peace, dearest; for you have the power… 
The Athenians gave Demetrios an arrival that was fit for a god, burning incense on altars and making offerings to their new deified king. It must be pointed out that as time passed by, he did some other things that the Athenians did not approve of, and as a consequence they revoked their adoration of him. It seems that in the days before Jesus, divinity could be stripped away from human beings just as easily as it was granted. Perhaps the best known examples of God-men are the divine honours bestowed upon the rulers of the Roman Empire, starting with Julius Caesar. We have an inscription dedicated to him in 49 BCE discovered in the city of Ephesus, which says this about him :
Descendant of Ares and Aphrodite
The God who has become manifest
And universal savior of human life
So Julius Caesar was God manifest as man, the saviour of mankind. Sound familiar? Now prior to Julius Caesar, rulers in the city of Rome itself were not granted divine honours. But Caesar himself was – before he died, the senate approved the building of a temple for him, a cult statue, and a priest. Soon after his death, his adopted son and heir, Octavian, promoted the idea that at his death, Caesar had been taken up to heaven and been made a god to live with the gods. There was a good reason that Octavian wanted his adopted father to be declared a God. If his father was God, then what does that make him? This deification of Caesar set the precedent for what was to happen with the emperors, beginning with the first of them, Octavian himself, who became “Caesar Augustus” in 29 BCE. There is an inscription that survives from his lifetime found in the city of Halicarnassus (modern Turkey), which calls Augustus :
…The native Zeus
and Savior of the human race
This is yet another example of a divine saviour of mankind. Now Octavian happened to also be the “son of God” by virtue of his divine father Julius Caesar. In fact Octavian became known as ‘Divi filius’ (“Son of the Divine One”). These, of course, are all titles widely used by Christians today to describe Jesus. We must realise that the early Church did not come up with these titles out of the blue, they are all things said of other men before they were said of Jesus. For early Christians, the idea was not that Jesus was the only person who was ever called such things, this is a misconception. The concept of a divine human being who was the saviour of mankind was a sort of template that was applied to people of great power and authority. We’ve seen that the history of paganism is littered with such examples, and Jesus was just another divine saviour in a long list of divine saviours that had preceded him.
HOW ISLAM ELIMINATED IDOLATRY
Pre-Islamic Arabia was a dreadful place to live in. Slavery was an economic institution with male and female slaves being bought and sold like animals. Illiteracy was common among the Arabs, as were alcoholism and adultery. Those with power and money took advantage of the poor by charging extremely high interest on loans. Arabia was a male-dominated society; men could marry any number of women. When a man died, his son “inherited” all his wives except his own mother. Women had virtually no legal status, for example they had no right to possess property and had little to no inheritance rights. Female infanticide was widely practiced with daughters often being buried alive.
It was not only the rights of human beings that were violated, but also the rights of God. The Arabs were a highly idolatrous people. The idolatry of pre-Islamic Arabia seeped into every facet of day-to-day life. Idols adorned their places of worship. Today the Ka’aba, situated in Saudi Arabia and the holiest place of worship for Muslims, contains neither idols nor images. But before Islam, the pagan Arabs housed 360 different idols in the Ka’aba. Idols were their travel partners whenever they set out on a journey, for the Arabs were very superstitious and believed that they would provide protection in a land plagued by highway robbery and kidnapping. They were also the source of their livelihoods, so central was the Ka’aba to idolatry that pagans from all over Arabia would make pilgrimage there.
In just 23 years, Islam managed to completely reform not only the social ills of Arabian society, but also its idolatry, taking people away from the worship of carved images and stones to the worship of the One true God of Abraham. This is the testimony of Ja’far bin Abi Talib, who was a contemporary of Prophet Muhammad (peace be upon him). Here he informed the king of Abyssinia about the condition of his people and the positive change that Islam brought for them:
O King, we were an uncivilised people, worshipping idols, eating corpses, committing abominations, breaking natural ties, treating guests badly, and our strong devoured our weak. Thus we were until God sent us an apostle whose lineage, truth, trustworthiness, and clemency we know. He summoned us to acknowledge God’s unity and to worship Him and to renounce the stones and images which we and our fathers formerly worshipped. He commanded us to speak the truth, be faithful to our engagements, mindful of the ties of kinship and kindly hospitality, and to refrain from crimes and bloodshed. He forbade us to commit abominations and to speak lies, and to devour the property of orphans, to vilify chaste women. He commanded us to worship God alone and not associate anything with Him, and he gave us orders about prayer, almsgiving, and fasting. We confessed his truth and believed in him, and we followed him in what he had brought from God, and we worshipped God without associating aught with Him. 
Just how did the Qur’an go about winning the hearts and minds of people, completely transforming every level of Arabian society in such a short space of time? The Qur’an takes into account the psychology of its audience, which is demonstrated in its use of language. In defining the relationship between God and mankind, the Qur’an avoids terms like “Father” when referring to God and “sons of God” when referring to human beings. Such language can be easily misunderstood, especially in the minds of those who come from a background of idolatry and are used to interpreting such language literally. There are even those who might take advantage of such ambiguous language in Scripture, by interpreting it in such a way as to try and justify idolatry. The Qur’an warns mankind against using ambiguity as the foundation for our beliefs:
It is He who has sent this Scripture down to you [Prophet]. Some of its verses are definite in meaning – these are the cornerstone of the Scripture – and others are ambiguous. The perverse at heart eagerly pursue the ambiguities in their attempt to make trouble and to pin down a specific meaning of their own [3:7]
The Qur’an confirms that those who believe that Jesus is the literal Son of God are imitating an ancient pagan concept: “The Christians said, ‘The Messiah is the son of God’: they said this with their own mouths, repeating what earlier disbelievers had said.” [9:30] When the Qur’an defines the relationship between God and mankind, it instead uses terms like Creator when referring to God, and we as the creation. Such terms leave no room for confusion and clearly distinguish between what is God and what is not – everything else. Such careful use of language shows the wisdom of the Qur’an’s author and the insight they have into the human condition. Our Creator knows the inner thoughts of man: “We created man – We know what his soul whispers to him: We are closer to him than his jugular vein.” [50:16]
THE PURITY OF ISLAMIC MONOTHEISM THROUGH THE AGES
The foundations of Muslim belief were set during the lifetime of Prophet Muhammad. The message given to Muhammad, the Qur’an, represents perfection in the way of life for human beings to live: “Today I have perfected your religion for you, completed My blessing upon you, and chosen as your religion Islam…” [5:3] If something has been perfected then it cannot be further improved, and so there is no need to send any additional messengers or messages to mankind.
As well as setting a solid theological foundation early on, the Qur’an and Sunnah (teachings and actions of Prophet Muhammad) expressly forbid believers from adding to the religion of Islam. The Qur’an warns mankind against inventing doctrine and claiming it is from God:
So woe to those who write the “scripture” with their own hands, then say, “This is from God,” in order to exchange it for a small price. Woe to them for what their hands have written and woe to them for what they earn. [2:70]
Likewise the Sunnah also warns mankind against tampering in the religion. Prophet Muhammad said: “Whoever tells lies about me deliberately, let him take his place in Hell.” 
When one studies history, you will find that Islamic monotheism, known as ‘tawheed’ in Arabic, has undergone no historical evolution in the nearly 1,500 years that have passed since the Qur’an was first revealed to Prophet Muhammad. Muslims hold to the same creed to this very day. All who have tried to introduce something new into the creed of Islam have been rejected purely on the basis that it was not taught by Prophet Muhammad. This is the standard that Muslim scholars have held to since the beginning of Islam. These strict standards have been built into the religion since its inception, preserving the purity of its teachings such as Tawheed.
It’s important to note that like with any religion, various sects and innovations have sprung up throughout Islamic history. Prophet Muhammad himself foretold that this would be the case: “My nation will split into seventy-three sects, all of whom will be in Hell except one group – (those who follow) that which I and my companions follow” . However, the key point is that thanks to the Sunnah, a Muslim alive today in the 21st century is able to avoid all innovations and stay upon the correct, pure understanding of Tawheed as it was understood by Prophet Muhammad and his companions in the 7th century.
1 – John William Charles Wand. 1955. The Four Great Heresies, p. 39.
2 – Justin Martyr, The First Apology, Chapter 21.
3 – Dr. H Wolfson, The Philosophy of the Church Fathers, pp. 361 – 363.
4 – Angelos Chaniotis, The Ithyphallic Hymn for Demetrios Poliorcetes and Hellenistic Religious Mentality, p. 160.
5 – Iris Sulimani, Diodorus’ Mythistory and the Pagan Mission: Historiography and Culture, p. 288.
6 – Hans-Josef Klauck, Religious Context of Early Christianity: A Guide To Graeco-Roman Religions, p. 296.
7 – The Life of Muhammad, A Translation of Ishaq’s Sirat Rasul Allah, translation by A. Guillaume, 2004, pp. 151 – 152.
8 – Sahih Bukhari, Hadith #1229.
9 – Tirmidhi, Hadith #2641.