This essay will attempt to provide a quick overview of the reasons why Christians believe in the Trinity—a word that never appears in the Bible. I make no claim to be exhaustive in the passages I cite and this is certainly not a scholarly treatise. It is just a quick overview of the topic.
The essay assumes the Judeo/Christian belief that God is one (Deuteronomy 6:4; Mark 12:29; Romans 3:30; 1 Corinthians 8:4, 6; Galatians 3:20; 1 Timothy 2:5; James 2:19). Upon that foundation, the paper will show that 1) The New Testament teaches the deity of Jesus. This is by far the longest section of the paper since the deity of Jesus is the aspect of the Trinity which comes under the strongest attack, 2) The New Testament teaches the deity and personality of the Holy Spirit (i.e. that the Holy Spirit is a sentient being and not just an impersonal force like gravity, magnetism, etc.) 3) That the New Testament distinguishes between Father, Son and Spirit. 4) That the theological doctrine of Trinity best accounts for the biblical data.
DEITY OF JESUS
The question we are addressing first is, what does the New Testament teach about Jesus?
Synoptic Gospels (Matthew, Mark and Luke)
According to most scholars, Mark was the first biblical gospel to be written. The writer of Mark begins his gospel with quotes from Malachi 3:1 and Isaiah 40:3 about how a messenger would go before and prepare the way for Yahweh (God). In the verses that follow (Mark 1:4-9), Mark introduces John the Baptist who is preparing the way for Jesus. Mark sees John the Baptist and Jesus as the fulfillment of the prophecies about the messenger (John) preparing the way for God (Jesus).
Messenger -------> Yahweh
John the Baptist --> Jesus
Now in case that parallel was lost on some readers, Mark then immediately writes about how Jesus is baptized while the Spirit of God descends on him like a dove, and a voice comes from the heavens declaring that Jesus is “my beloved Son.” God the Spirit descends on God the Son while God the Father speaks from heaven. This declaration from God that Jesus is his Son is repeated later in Mark 9:7.
It is important to note that “Son of God” (as Jesus is called in most ancient texts of Mark 1:1) can mean different things depending on the context. In Job, “sons of God” is a reference to angels. Sometimes in the Old Testament Israel was said to be God’s son. Sometimes the king was said to be God’s son.
Mark, however, makes it clear that Jesus is the son of God is a much more significant sense. In Mark 2:1-12 Jesus heals a paralyzed man and tells him, “My son, your sins are forgiven (Mark 2:5). Note that Jesus is not saying that this man has personally offended Jesus therefore Jesus forgives him of this offense. Jesus was not even acting as a priest by assuring the man of God’s forgiveness. Mark wants readers to understand that Jesus was declaring that this man’s sins are forgiven. In a Jewish context—and Jesus was a Jew, living with Jews and ministering to Jews—only God could forgive sins!
According to Mark, the people understand exactly what Jesus was claiming because they complain saying, “He is blaspheming! Who can forgive sins but God alone” (Mark 2:7). Jesus then confirms that they have not misunderstood him. He tells them that he said this so they would know that he has authority “on earth” to forgive sins.
Mark was clearly intending his readers to understand that Jesus was claiming to do something only God could do. But words are cheap. Anyone can claim to forgive sins, right?. According to Mark, the paralyzed man then got up an walked! (Mark 2:9-12).
To emphasize this point further--i.e the point that Jesus claimed to do what only God could do-- Mark then tells a story about how Jesus had a run-in with Pharisees about picking grain on the Sabbath day (Mark 2:23-28). Jesus claims that he is Lord over the Sabbath.
This would have been a truly shocking claim, something that would have made Jesus sound out of his mind. After all, God instituted the Sabbath day! Only God was above the Sabbath. Yet according to Mark, Jesus claimed to be Lord over the Sabbath. Mark clearly wants readers to understand that Jesus was placing himself in the position of God.
Mark later writes about how Jesus teaches people about Jewish dietary laws. Jesus says, “Do you not see that whatever goes into a person from outside cannot defile him, since it enters not his heart but his stomach and is expelled?” Mark then adds his own parenthetical, theological explanation, “Thus he declared all foods clean” (Mark 7:18-19).
This is another shocking statement. According to the Jewish Bible (the Christian Old Testament) God had established those dietary laws. Only God could annul those laws. Mark clearly wants the reader to understand that Jesus was placing himself in the position of God.
But there is more. In the Jewish Bible, God alone was the source of salvation in a spiritual sense, but according to the Gospels, Jesus claims that prerogative. In Mark 10:17 a man asks Jesus how to have eternal life and Jesus final answer is “follow me” (Mark 10:21).
This is remarkable. No prophet—not Moses, not Elijah, not Isaiah—no prophet would have said that the way to have eternal life was to follow them. That is because eternal life is found only in God. The prophets all pointed people to God. Only Jesus says the way to eternal life is to follow him. Mark wants readers to understand that Jesus was putting himself in the place of God!
But Mark is not done yet. Just before his death Jesus has a last supper with his disciples. He takes the cup of wine and tells his disciples, “This is my blood of the covenant which is poured out for many” (Mark 14:22-25).
The covenant to which Jesus is referring is from Jeremiah 31:31 which specifically declares that it will be Yahweh (God) who makes this new covenant. Mark wants the reader to understand that Jesus is, once again, putting himself in the place of God. It is no wonder some thought he was out of his mind (Mark 3:21)!
Finally, some four hundred years before Jesus’ time, Zechariah prophesied to Israel, “Behold your king is coming to you; righteous and having salvation is he, humble and mounted on a donkey, on a colt, the foal of a donkey” (Zechariah 9:9). Zechariah tells us exactly who the king is: “And Yahweh will be king over all the earth” (Zechariah 14:9, cf. 14:17). Mark presents Jesus as deliberately fulfilling a prophecy about God coming to visit his people (Mark 11:1-10).
These views were not just expressed in the Gospel of Mark, however. Luke (7:47-50) and John (8:24) also claim that Jesus could personally grant forgiveness of sins.
Matthew (12:8) and Luke 6:5 also claim that Jesus was Lord over the Sabbath.
Matthew (25:21-46) and Luke (19:11-27) claim that people’s eternal destiny would be dependent on Jesus (cf. John 3:15, 10:19).
According to Matthew (13:24-30; 36-43; 25:31-46) and Luke (3:16-17; 17:23-37) Jesus claimed that he would personally judge the world claimed that he would personally judge to world; a task that belonged to God alone.
And all four Gospels (Matthew 21:1-11; Mark 11:1-10; Luke 19:28-44; John 12:12-19) tell of Jesus riding into Jerusalem in fulfillment of the prophecies about God visiting his people. It is clear what the synoptic Gospel writers want readers to understand about Jesus.
Gospel of John
There is really not much dispute among scholars that the Gospel of John intends to present Jesus as God incarnate. Even most theologically liberal biblical scholars understand that this is what John is intending to say. They just don't believe it. The only ones who think John was not presenting Jesus as God are usually those with a theological axe to grind, for example, cults like Jehovah’s witnesses.
John begins his gospel declaring, “In the beginning was the Word, and the Word was with God and the Word was God. He was in the beginning with God. All things were made through him, and without him was not anything made that was made” (John 1:1-3).
Then John declares that this “Word” which was "with God and was God," became human and lived with us (John 1:14). He is the one to whom John the Baptist bore witness (John 1:15), the one who is specifically identified as Jesus in John 1:29. He is the one whom John's Gospels calls, “the only God who is at the Father’s side” (John 1:18).
Jehovah’s witnesses try to avoid this teaching by mistranslating John 1:1. Their New World Translation of John 1:1 reads, “In [the] beginning the Word was, and the Word was with God, and the Word was a god.”
Jehovah’s witnesses insist that since the second occurrence of God/god in John 1:1 is not preceded by the definite article (i.e. “the”) in Greek, it must (MUST) be translated as “a god” not God with a big G (Note: the Greek article is often not translated into English so it usually does not appear in English Bibles).
The translators of the Jehovah's Witness Bible are factually in error in this verse. It is an absolute fact that the absence of the Greek article does not always mean the subject is indefinite. There is a grammatical reason why John could not add the definite article to the second occurrence of "God" in John 1:1 (suffice it to say that adding the definite article before God would make it impossible in Greek to determine the subject of that clause).
Anyway, it is pretty hard to see how the translators of the New World Translation could be ignorant of the fact that the lack of a definite article does not always make the subject indefinite. This is because there are at least thirteen places in John's Gospel alone (John 1:6, 12, 13, 18; 3:21; 8:54; 9:16; 9:33; 13:3; 16:30; 19:7; 20:17 (twice!) where the Greek word for God (theos) appears without the Greek definite article and yet the Jehovah’s Witnesses translators translate the word with a big G (God) anyway! In fact, in John 6:45 the word Theos (God) appears without the definite article and yet the New World Translation translates it not as "a god" but as "Jehovah!" Apparently Jehovah's Witnesses only follow their own translation rules where it fits their doctrine.
The fact that John attributes deity to Jesus is not just seen in chapter one, however. According to John’s gospel, people’s eternal destiny would be dependent on Jesus:
“For God so loved the world that he gave his only Son that whoever believes in him should not perish but have eternal life” (John 3:16).
“For this is the will of my Father, that everyone who looks on the Son and believes in him should have eternal life, and I will raise him up on the last day” (John 6:40).
“I am the living bread that came down from heaven. If anyone eats of this bread, he will live forever” (John 6:51).
“Whoever feeds on my flesh and drinks my blood has eternal life and I will raise him up on the last day” (John 6:54).
“I am the door, if anyone enters by me, he will be saved…” (John 10:9).
In a first century Jewish context only God could save in a spiritual sense. Only God could grant eternal life. The writer of John’s Gospel clearly wants readers to understand that Jesus is God.
There is more. According to John 8:58 Jesus claimed, “Truly, truly I say to you, before Abraham was, I AM.” No only was Jesus claiming to have existed before his own birth—a claim he also makes in John 17:5—many scholars note that the phrase “I AM” is the name of God, Yahweh. This claim may be why according to the text, Jesus enemies “picked up stones to throw at him” (John 8:58).
Some would argue that maybe Jesus’ critics misunderstood him. Even if that were true (it’s not) it is still quite clear that John wants us to understand why they were preparing to stone him.
According to John 10:30 Jesus said, “I and my Father are one” (John 10:30) Some have dismissed this as the same kind of oneness that Christians experience. The Jewish audience to whom Jesus was addressing, however, understood that Jesus was talking about being one with God in a much deeper sense which is why they prepared to stone him for blasphemy saying it was because "you being a man, make yourself God."
I once spoke to a Jehovah’s Witness about this passage and his response was to say that all Jews were liars so why would I believe what they said about Jesus? Aside from the fact that this was an incredibly racist and anti-Semitic statement, we must note that the writer of the Gospel of John was Jewish. I guess it didn’t occur to this "witness against Jehovah" that if all Jews are liars then we can’t trust the Gospel of John either because it was written by a Jew! But this Jehovah’s Witness was just trying to re-interpret (twist) the Gospel of John. He would never argue that we should tear it out of our Bible.
The writer of John clearly wants readers to understand that Jesus was claiming oneness with God in a way that Jesus’ Jewish audience considered blasphemous. In the words of Jesus’ enemies, “It is not for a good work that we are going to stone you but for blasphemy, because you being a man, make yourself God” (John 10:33).
John begins his gospel proclaiming the deity of Jesus and he ends it the same way. In 20:24-29 “doubting Thomas” sees the risen Jesus and exclaims “My Lord and My God (John 20:28)! It is important to note that Jesus does not rebuke Thomas for this worship but rather blesses him! There can be no serious doubt that the writer of John’s Gospel wants readers to understand that Jesus is the very incarnation of God!
In the Old Testament salvation, in a spiritual sense was found only in God, but Acts 4:12, speaking of Jesus, says, “and there is salvation in no one else; for there is no other name under heaven that has been given among men by which we must be saved.” Acts 16:31 reinforces this saying “Believe in the Lord Jesus and you will be saved.”
In the Jewish Bible God was the final judge of the living and the dead but Acts 10:42 says that Jesus “is the One who has been appointed by God as judge of the living and dead.”
In Acts 2:21 Peter quotes from Joel 2:32 which says that “…everyone who calls upon the name to the Lord [Yahweh] will be saved.” Peter applies this directly to Jesus, i.e. everyone who calls on the name of Jesus will be saved.
Paul is actually our very earliest witness to Jesus. Paul takes the passage in Joel 2:32 which says that “…everyone who calls upon the name to the Lord [Yahweh] will be saved” and applies that directly to Jesus (Romans 10:13, 17), i.e that everyone who calls on the name of Jesus will be saved.
It is probable that Paul was also intending to directly attribute deity to Jesus in Romans 9:5 which could be translated, “from whom is Christ according to the flesh, who is God over all, blessed forever.” Or, as the New Living Translation puts it, “Christ himself was a Jew as far as his human nature is concerned. And he is God, who rules over everything and is worthy of eternal praise” (NLT).
According to Paul it is through Jesus that all things exist (1 Cor. 8:6). Paul repeats this teaching in Colossians 1:16-17 where he says that it was by Jesus that “all things were created, both in heavens and on earth….”
As a good Rabbi, Paul knows full well that God is the only creator. No wonder Paul writes that Jesus “existed in the form of God” (Philippians 2:6) and that “in Him the fullness of Deity dwells in bodily form” (Colossians 2:9).
In Titus 2:13 Paul writes, “Looking for the blessed hope and the appearing of the glory of our great God and Savior, Jesus Christ.” There is a way, in Greek in which Paul could have distinguished between Father and Son in this passage, but the way he writes this makes it pretty clear that he intended to call Jesus “our great God and Savior.”
Hebrews and General Epistles
The Book of Hebrews refers to Jesus as the very “radiance of the glory of God and the exact imprint of his nature” and says that Jesus “upholds the universe by the word of his power” (Hebrews 1:3).
According to Hebrews, quoting from Psalm 2:7, God himself called Jesus his Son (Hebrews 1:5). According to Hebrews God said to Jesus, “Your throne, O God, is forever and ever” (Hebrews 1:8). It is clear that the author of Hebrews intends to teach the deity of Jesus.
The deity of Jesus is also taught in First and Second Peter. Isaiah 8:13 says “The LORD [Yahweh] of Hosts, him you shall regard as holy…” First Peter 3:15 says Jesus is the one we should regard as holy!
Second Peter 1:1 speaks of “the righteousness of our God and Savior Jesus Christ.” There is a way in Greek in which Peter could have made a distinction between our God, and our Savior Jesus Christ but Peter does not do this. He intends to call Jesus, “Our God.”
According to Revelation 22:13 Jesus says, “I am the alpha and omega, the first and the last, the beginning and the end,” but Revelation 1:8 says it was the Lord God who was the alpha and omega.
What is particularly interesting about these passages is that they are also found in the Jehovah’s Witness’s New World Translation which goes to great lengths to remove any trace of Jesus’ deity. They missed one. The New World Translation translates Revelation 1:8 as “I am the alpha and omega, says Jehovah God.” But at the end of Revelation, the alpha and omega is the one who is coming quickly (Revelation 22:12-13), identified specifically as Jesus in Revelation 22:16. Even the Jehovah’s Witnesses own translation teaches the deity of Jesus!
It is no wonder, therefore, that Jesus was also the object of worship in the New Testament...and remember, in a Jewish context only God was the object of worship! Paul says that “at the name of Jesus every knee will bow (Philippians 2:10). Paul exclaims that to Jesus “be glory forever and ever” (2 Timothy 4:18). Second Peter 3:18 also says that to Jesus “be glory, both now and to the day of eternity.” Hebrews 1:6 says of Jesus, “let all the angels of God worship him.” Revelation says that to Jesus “be the glory and dominion forever and ever” (1:5-6) and “To Him who sits on the throne, and to the Lamb [Jesus], be blessing and honor and dominion forever and ever…and the elders fell down and worshiped” (5:11-14).
After the New Testament
Is it possible, however, that we have misunderstood what the New Testament teaches about Jesus’ deity?
Not a chance! Those who wrote shortly after the New Testament understood exactly what the New Testament taught about Jesus!
Clement of Rome (AD 97), for example, described Jesus as the “majestic scepter of God” and the radiance of God’s majesty (Clement to the Corinthians, 16, 36).
Ignatius (AD 110) wrote about “our God, Jesus Christ” (to the Romans, 3; to the Ephesians, 18) and “Jesus Christ, our God” (to the Ephesians, Intro), and “stirring up yourselves by the blood of God (to the Ephesians, 1), and “God Himself being manifested in human form” (to the Ephesians, 19) and “servants of Christ our God” (to the Smyrneans, 10).
The letter of Barnabas—not the Barnabas of the Bible but some other Christian named Barnabas (AD 70-135), says, “…the Son of God was the divine Lord, and the future Judge of living and dead alike” (Chapter 7). The letter of Barnabas calls Jesus “the Lord of all the earth,” a title used in Joshua 3:13 to refer to God (5:1).
Justin Martyr (d. 163) writes that “…the Father of the universe has a Son; who also, being the first-begotten Word of God, is even God (First Apology of Justin LXIII).
The idea that Jesus was God is also found in ancient books known as the New Testament Apocrypha (not to be confused with the Catholic apocrypha which was written before the time of Jesus). Most New Testament Apocrypha were written from the second to fourth or fifth centuries AD. One of these books is the Acts of Andrew (4th cent.) which ways, “Andrew prayed thus: ‘I pray you, my God, Lord Jesus Christ….”
The Apocalypse of Peter” says, “… my Lord and God Jesus Christ” (Apocalypse of Peter, Ethiopic 16, 135 AD).
The “Acts of John” says, “Glory be to thee, my Jesus, the only God of truth” (Acts of John 43, 2nd-3rd c.).
The Ascension of Isaiah says, “and he who gave permission is thy Lord, God, the Lord Christ, who will be called Jesus on earth” (Ascension of Isaiah 5, 2nd c.).
In the Acts of Paul and Thecla we find, “My God, Jesus Christ” (Acts of Paul and Thecla, 185-195 AD).
The fact that these early Christians believed Jesus was God is also confirmed in secular sources.
The anti-Christian satirist, Lucian also wrote of Christians saying that they “worship” Jesus (Lucian early 100’s)
The Roman governor, Pliny the Younger (AD 112), for example, conducted an investigation of Christians and reported to the Roman emperor that they “were in the habit of meeting on a certain fixed day before it was light, when they sang in alternative verses a hymn to Christ, as to a god” (Letter to Emperor Trajan). Of course Pliny would write “to a god” instead of “to God” because Pliny didn’t believe in just one God.
By the way, contrary to the popular DaVinci Code, even writers of the so-called “lost gospels” believed Jesus was some kind of divine being. The “Teachings of Silvanus,” for example, says, “Know who Christ is…He is also God and Teacher. This one, being God, became man for your sake” (Teachings of Silvanus 110).
The “Letter of Philip” says, “according to the orders of our God Jesus” (Letter of Peter to Philip 133).
The “Trimorphic Protennoia says, “They blessed Perfect Son, the Christ, the only-begotten God” (Trimorphic Protennoia 38).
These “lost gospels” are not Christian documents. Contrary to Christianity, they generally believe that Jesus was one of many divine beings. The point the Da Vinci Code is factually in error whn it says that “these documents speak of Christ’s ministry in very human terms” (Brown, 234). The fact is that one of the very earliest controversies about Jesus was not about whether he was divine or not, but whether he was actually human or not!
All of this evidence, of course, does not prove that Jesus was God, but it does demonstrate rather conclusively that early Christians believed that Jesus was God and that they believed it hundreds of years before any church councils got together to discuss the issue.
THE HOLY SPIRIT
The Holy Spirit of God is called God in the Bible. For example, Acts 28:25-26 says that “The Holy Spirit was right in saying to your fathers through Isaiah the prophet…” What follows is a quote from Isaiah 6:8-9 which was spoken by God.
Similarly Hebrews 10:15-17 says, “And the Holy Spirit also bears witness to us…saying…” What follows are quotes from Jeremiah 31:31-34 which was spoken by God. The point is that the writers of Acts and Hebrews attribute to the Holy Spirit, words spoken in their original contexts by God.
The Deity of the Holy Spirit is confirmed by the fact that the Holy Spirit is said to have the attributes of God (Gen 1:2; Job 26:13; 1 Cor 2;9-11; Hebrews 9:14) and the Holy Spirit performs the works of God (Job 33:4; Ps 104:30; Luke 12:11-12; Acts 1:5; 20:28; 1 Cor 6:11; 2:8-11; 2 Peter 1:21).
The Holy Spirit is often called the “Spirit of God” (Genesis 1:2; Exodus 31:3; Numbers 42:2; First Samuel 10:10; 2 Chronicles 24:20; Job 33:4; Ezekiel 11:24; Romans 8:14, 15:19; 1 Corinthians 2:14; Ephesians 4:30; Philippians 3:3; 1 John 4:2).
We might conclude that the Spirit of God is just another way of saying “God” except that many passages specifically distinguish between God the Father, God the Son, and God the Spirit. This will be covered in a separate section below.
In the mean time, it is also important to note that according to the New Testament, the Holy Spirit is not just some impersonal force like gravity or magnetism. The Holy Spirit is a being who, like any sentient being has intellect, emotion and will (theologians use the word "person" for lack of a better term).
According to the New Testament, the Holy Spirit admonishes (Jn 16:8), teaches, (Jn 14:26; 16:13-15; 1 Jn 2:27), guides (Jn 16:13) speaks (Gal 4:6), intercedes (Rom 8:26), leads (Gal 5:18), appoints for service (Acts 13:2), regenerates (Jn 3:6), baptizes (1 Cor 12:13), fills (Eph 5:18) and glorifies Jesus (Jn 16:14). He is called a Helper, Comforter/counselor or advocate (Jn 14:6-17; 26; 16:7; 1 John 2:1-2). He can be grieved (Eph 4:30), quenched (resisted; 1 Thess 5:19), blasphemed (Matt 2:31) and lied to (Acts 5:3).
The point is that no one would speak about lying to a force like gravity, or grieving magnetism or blaspheming nuclear forces!
Although the word "spirit" in Greek is grammatically neuter meaning that you would expect that a neuter pronoun would be used to refer to the Spirit, the Holy Spirit is sometimes referred to with the masculine pronoun, "He." (e.g. John 14:16-17; 16:7-15).
In other words, the Bible usually refers to the Holy Spirit as a "He" rather than "it." The use of "He" does not mean the Holy Spirit is male (a spirit is neither male nor female), but the use of "He" does seem to indicate that the Holy Spirit is a personal being rather than an impersonal force.
So like any “person” the Holy Spirit has intellect (He can teach, guide, speak), emotion (He can be grieved), and will (He submits to the Father John 14:16-17; 26). The Holy Spirit is also God.
Distinction between Father, Son and Spirit
The Bible clearly make a distinction between God the Father, God the Son and God the Spirit.
For example, Matthew 3:16 clearly makes this distinction as does Mark 1:9-11 and Luke 3:21-22 where Jesus is baptized while the Spirit of God descends on him and the Father speaks from heaven. A distinction between Father, Son and Spirit is also clear from John 14:26 where Jesus says his Father will send the Spirit to the disciples.
Matthew 1:18 makes a distinction between the Holy Spirit and the unborn Jesus who is still in his mother’s womb. Jesus makes a distinction between himself and the Spirit in Matthew 12:28 and in John 14:7, 12-14.
Jesus distinguishes between the Father, Spirit and himself when he speaks of blasphemy against the Spirit as worse than blasphemy of him or the Father (Matthew 12:32; Mark 3:29), possibly because it is the Spirit who draws people to the Father and Son.
Luke 4:1 distinguishes between Jesus and the Holy Spirit saying that Jesus, being filled with the Spirit was led by the Spirit in the wilderness. Luke 11:13 is about how the Father will give the Holy Spirit to those who ask.
Paul seems to distinguish between the Spirit of God and God in 1 Corinthians 2:11.
The New Testament also make a distinction between the tasks the Father, Son and Spirit perform. For example, the Holy Spirit glorifies Jesus (John 16:14). The Bible never says that Jesus "glorifies the Holy Spirit."
The Spirit is “sent” by the Father (John 14:16-17, 26) and by the Son (John 16:7). The Bible never says the Spirit sends the Father although the does say the Spirit “led” Jesus (Luke 4:1). Jesus was crucified.
The Father and Spirit were not crucified.
Finally, in the New Testament, the Father speaks to Jesus (Matthew 3:17, 17:5; Mark 1:11, 9:2; Luke 3:22; 9:35) and Jesus prays to the Father (e.g. Matthew 26:39; Mark 14:35; Luke 22:42; John 17). Jesus is not praying to himself!
Is it possible that we have misunderstood our New Testament on the distinction between Father, Son and Spirit?
Not a chance!
The earliest church “fathers” writing right after the New Testament was written understood completely what the New Testament was teaching. Although Ignatius calls Jesus God, he distinguishes between Father and Son: “by the will of the Father and Jesus Christ our God.” (Ignatius, Letter to the Ephesians).
So does Justin, “…the Father of the universe has a Son; who also, being the first-begotten Word of God, is even God. (First Apology of Justin LXIII).
So does Irenaeus, “"and ‘the Word was with God…and the Word was God,’ of course, for that which is begotten of God is God.” (Against Heresies 1.8.5).
We also find the distinction between Father and Son in the Epistle to Diognetus, “he sent him in gentleness and meekness, as a king might send his son who is a king; he sent him as God” (to Diognetus 7).
In fact, as early as the Didache, which could have been written any time between about AD 70 and 150, we find a full-blown statement of the Trinity, at least 300 years before any church councils met to discuss the issue: “baptize in the name of the Father and of the Son and of the Holy Spirit in running water. But if you have no running water, then baptize in some other water…But if you have neither, then pour water on the head three times in the name of the Father and Son and Holy Spirit” (Didache 7)
Some in the early church argued that there is one God who appeared in three “modes”: Father in the Old Testament, Jesus in the early first century AD, and the Holy Spirit after the resurrection of Jesus. There is a modern version of this called “Jesus only” which denies the Trinity, and teaches that Jesus sometimes manifested himself as God, sometimes as Jesus and sometimes as the Spirit.
The ancient version of this became known as Modalism or Sabellianism. It was condemned as heresy because it just doesn’t account for the biblical data which not only presents Father, Son, and Spirit at the same time and place (e.g. the Baptism of Jesus), but does not preserve the Biblical distinctions between Father, Son and Spirit.
Cultists and some critics will challenge this evidence, of course. They have to! They have an agenda to preserve. It would be relatively easy to pick apart individual pieces of the evidence above and entire books have been written which interact with all the arguments. One of the best places to start would be the book, entitled, Jesus as God; the New Testament Use of Theos in Reference to Jesus by Murray Harris (Baker, 1992). The book is an indepth, scholarly evaluation of the New Testament passages that attribute deity to Jesus. It argues from the original languages but even those who don’t know Hebrew or Greek can profit from the book.
Anyway, it is for all of the reasons above and more—this is by no means a scholarly or exhaustive study!—that orthodox Christians have concluded that the Bible teaches there is ONE and only ONE God (Deuteronomy 6:4; Mark 12:29; Romans 3:30; 1 Corinthians 8:4, 6; Galatians 3:20; 1 Timothy 2:5; James 2:19) who exists eternally in three “persons,” Father, Son and Spirit. The Bible doesn't have a name for this phenomena so theologians chose to call it the Trinity (I think Tri-unity may have been a better term).
Whenever you hear the tired old argument that “the word Trinity” doesn’t even appear in the Bible” know and understand that the critic is grasping at straws in desperation. The argument is completely irrelevant. All orthodox Christians—Catholic, Protestant and Eastern Orthodox—understand that “trinity” is a word developed by later Christians to describe a phenomena found in the Bible. The fact that the word itself is not found in the Bible says absolutely nothing about whether the doctrine is found in the Bible or not.
It is true, of course, that the concept of Trinity is hard to understand and even harder to explain, but this is what the Bible teaches. Many analogies have been proposed, like for example, the egg which is one, and yet composed of egg whites, a shell and yoke. But a yoke is just part of an egg and Jesus is not just part of God.
All analogies break down. The best one I’ve come up with is from science fiction. Being a Star Trek Next Generation fan, I sometimes use the “Borg” as an analogy. In Star Trek Next Generation the Borg is an alien being that resides in a gigantic cube shaped object. The Borg consists of thousands of beings appearing like grotesque-looking people, but, the show is quick to explain, these are not thousands of Borgs. The Borg is one.
Each individual is distinct and yet intimately connected with every other individual. They can hear each others thoughts and function as one organism. If they conquered the Enterprise, for example, one might be on the bridge interacting with the captain, one might be in the engineering section controlling the engines and one might be in the transporter room controlling access to the Enterprise. Three individuals with different tasks but yet so intimately connected that they function, and in fact are, one organism.
But again, all analogies break down. Star Trek is science fiction. God is science fact. In Star Trek the Borg is evil whereas God is good. In Star Trek the Borg consists of thousands of individuals where as God exists in three persons. The Borg’s power is finite where as God is all powerful, etc. And yet, I think the analogy may help to understand the concept of One God who exists eternally as Father, Son, and Spirit.
The fact is that we worship a Creator who created a universe so indescribably huge and complex (from incredibly complex micro-organisms to unimaginably gigantic galaxies) that human beings do not even begin to comprehend a tiny part of this creation. This being the case, do you suppose there might be some things about our awesome Creator that our human minds just do comprehend?
Imagine, for example, trying to explain a long distance cell phone call to someone from the 1700’s. They wouldn’t even understand the concept of telephones, much less cell phones. If you tried to explain cell phones to them, they wouldn’t understand microscopic circuits, or frequencies, or satellites or electronics or liquid crystal displays (LCD) or even plastic! In other words, they wouldn’t even understand the concepts necessary to understand the principles behind cell phones!
How much less do we understand God! So when God reveals himself as ONE God eternally existing in Father, Son and Spirit, Christians believe it even if we can’t adequately explain it.