There are two primary reasons for believing that God is an individual person. First, the Old Testament is unabashedly monotheistic. Monotheism was something which set the Jews apart from their neighboring nations.
Deut 6:4 (NASB)
Hear, O Israel! The Lord is our God, the Lord is one!
Consequently, Christians are also monotheists. Not only do they typically, like Jesus, believe the Old Testament to be true, but monotheism is also confirmed in the New Testament.
1 Cor 8:4-6 (NASB)
Therefore concerning the eating of things sacrificed to idols, we know that there is no such thing as an idol in the world, and that there is no God but one. For even if there are so-called gods whether in heaven or on earth, as indeed there are many gods and many lords, yet for us there is but one God, the Father, from whom are all things and we exist for Him; and one Lord, Jesus Christ, by whom are all things, and we exist through Him.
Rom 16:26-27 (NASB)
but now is manifested, and by the Scriptures of the prophets, according to the commandment of the eternal God, has been made known to all the nations, leading to obedience of faith; to the only wise God, through Jesus Christ, be the glory forever. Amen.
1 Tim 2:5-6 (NASB)
For there is one God, and one mediator also between God and men, the man Christ Jesus, who gave Himself as a ransom for all, the testimony given at the proper time.
The second reason for believing that God is an individual person is because we, as humans, are each an individual person, and we are made in the image and likeness of God.
Gen 1:26 (NASB)
Then God said, “Let Us make man in Our image, according to Our likeness; and let them rule over the fish of the sea and over the birds of the sky and over the cattle and over all the earth, and over every creeping thing that creeps on the earth.”
Burden of Proof
We are given logical minds so that we can think and understand both our universe and its creator. On the face of it, the doctrine of the Trinity seems illogical. How can Jesus be God's Son and also God at the same time? How can he be fully human and fully God at the same time? How can three equal one? (Obviously Trinitarians have explanations for these things.)
As such, logically speaking, the burden of proof lies on the Trinitarians to adequately prove that the doctrine of the Trinity is true. In the absence of a convincing argument in support of the Trinity, a single person in the Godhead is the natural default doctrine. If there is no good reason to believe that the Father and the Son are one God, it is logical to assume that they are separate beings (just as it is logical to assume that Moses only had two arms, unless there is a good reason to believe that he had three).
Therefore, unitarian (in the lower-case, non-trinitarian sense of the word) arguments usually revolve around Trinitarian proof-texts. The aim of their arguments is to show that passages such as John 1:1 do not need to be interpreted in the Trinitarian way. From their perspective, if they can show that there are reasonable non-trinitarian interpretations for all of the Trinitarian proof-texts, then their cause is won. For that reason, most Unity vs. Trinity debate is focused on passages which would typically be more favorable to the doctrine of the Trinity.
Scriptural Support for Unity
Finding verses that directly teach the doctrine of Unity is problematic because there is very little agreement, among non-trinitarians in some key areas. For instance, someone who believes that Jesus was the first creature created in God's creation will point to different verses to support their doctrine than someone who believes that Jesus did not exist until his birth.
So far, I have described two categories of scripture which are used in Unity vs. Trinity debates:
- Verses traditionally used as proof-texts for the Trinity, but are interpreted differently
- Verses which can be interpreted to support disparate non-trinitarian beliefs
However, there is a third category of verses on which most unitarians would typically agree in their interpretation:
#3. Verses which can be interpreted to contradict various doctrines of the Trinity
This third category of verses does nothing, per se, to prove the doctrine of unity, but it does provide more doubt, which helps to bolster the unitarian's position that their interpretation of the first category of verses should be taken more seriously. Compiling a comprehensive list of all of the verses in this third category of scripture is daunting, if not impossible. However, I will attempt to provide you with a list of some examples which show the various angles of attack which can be made.
Jesus Is Inferior to the Father
Orthodox Trinitarian doctrine teaches that the three persons of the Trinity are equal. They each have different roles and positions, but they all share the same authority and worth. There are several ways in which Jesus' inferiority to the Father may be argued. One way in which this is argued is to show that the Father is Jesus' God.
2 Cor 1:3 (NASB)
Blessed be the God and Father of our Lord Jesus Christ, the Father of mercies and God of all comfort
See also Eph 1:3 and 1 Pet 1:3.
Hebrews 1:8-9 (NASB)
But of the Son He says, “Your throne, O God, is forever and ever, and the righteous scepter is the scepter of His kingdom. You have loved righteousness and hated lawlessness; Therefore God, Your God, has anointed You with the oil of gladness above Your companions.”
In human terms, you can't get much more superior to someone than by being their God. It logically follows, then, that if Jesus has a God, he must be inferior to Him.
Another way to show Jesus' inferiority is with verses like the following, which show that God only gave partial authority to His Son:
1 Cor 15:27-28 (NASB)
For He has put all things in subjection under His feet. But when He says, “All things are put in subjection,” it is evident that He is excepted who put all things in subjection to Him. When all things are subjected to Him, then the Son Himself also will be subjected to the One who subjected all things to Him, so that God may be all in all.
Non-trinitarians would argue that this verse clearly contradicts the Trinity. How could Jesus be God if this verse is going out of it's way to say that Jesus is subject to God, and God is not subject to Jesus, so that "God may be all in all". This sentiment is repeated in other passages, for instance:
Eph 4:5-6 (NASB)
one Lord, one faith, one baptism, one God and Father of all who is over all and through all and in all.
Similarly, there are verses which show that, what authority Jesus did have, was given to him by the Father, for instance:
John 17:1-4 (NASB)
Jesus spoke these things; and lifting up His eyes to heaven, He said, “Father, the hour has come; glorify Your Son, that the Son may glorify You, even as You gave Him authority over all flesh, that to all whom You have given Him, He may give eternal life. This is eternal life, that they may know You, the only true God, and Jesus Christ whom You have sent. I glorified You on the earth, having accomplished the work which You have given Me to do.
And:
Acts 2:36 (NASB)
Therefore let all the house of Israel know for certain that God has made Him both Lord and Christ—this Jesus whom you crucified.
See also Luke 1:32.
Another way to show that Jesus is inferior is with verses, such as the following, which show that Jesus was the servant of God. In any normal understanding of the word, a servant is inferior to his master.
Acts 4:30 (NASB)
while You extend Your hand to heal, and signs and wonders take place through the name of Your holy servant Jesus.
And:
1 Cor 11:3 (NASB)
But I want you to understand that Christ is the head of every man, and the man is the head of a woman, and God is the head of Christ.
God Gave Jesus His Position
There are some verses which describe how, after Jesus accomplished His mission, God exalted Jesus, glorified Him, and gave Him a new title and position.
Phil 2:9-11 (NASB)
For this reason also, God highly exalted Him, and bestowed on Him the name which is above every name, so that at the name of Jesus every knee will bow, of those who are in heaven and on earth and under the earth, and that every tongue will confess that Jesus Christ is Lord, to the glory of God the Father.
Acts 5:30-32 (NASB)
The God of our fathers raised up Jesus, whom you had put to death by hanging Him on a cross. He is the one whom God exalted to His right hand as a Prince and a Savior, to grant repentance to Israel, and forgiveness of sins. And we are witnesses of these things; and so is the Holy Spirit, whom God has given to those who obey Him.
Eph 1:20-23 (NASB)
which He brought about in Christ, when He raised Him from the dead and seated Him at His right hand in the heavenly places, far above all rule and authority and power and dominion, and every name that is named, not only in this age but also in the one to come. And He put all things in subjection under His feet, and gave Him as head over all things to the church, which is His body, the fullness of Him who fills all in all.
If Jesus were God, why would the Father need to assign these things to Him?
Jesus' Will Is Different Than That of the Father
Traditional Trinitarian belief is that all three persons of the Godhead share the same nature, purpose, and will. However, in His prayer in the garden of Gethsemane, Jesus admitted that his will was different than his Father's will.
Matt 26:39 (NASB)
And He went a little beyond them, and fell on His face and prayed, saying, “My Father, if it is possible, let this cup pass from Me; yet not as I will, but as You will.”
Jesus said similar things in passages such as John 5:30 and John 6:38.
It could be said that any time Jesus is petitioning God for something, in any of His prayers, it is a demonstration of his separate will.
Heb 5:7 (NASB)
In the days of His flesh, He offered up both prayers and supplications with loud crying and tears to the One able to save Him from death, and He was heard because of His piety.
See also John 11:40-41 and John 17.
Jesus Is Not Omniscient
If Jesus is God, then he should be all-knowing, because God is all-knowing. However, Jesus said that he does not know when he will return. He said that only the Father knows that information.
Matt 24:36 (NASB)
But of that day and hour no one knows, not even the angels of heaven, nor the Son, but the Father alone.
Jesus Died and Became Sin
The Bible is clear that God is holy. He is far from sin. However, when Jesus died, the Bible tells us that he took the sin of the world upon himself.
2 Cor 5:21 (NASB)
He made Him who knew no sin to be sin on our behalf, so that we might become the righteousness of God in Him.
Even most Trinitarians concede that, due to sin, Jesus became separated from God on the cross. Most agree that that is why Jesus cried out "My God, My God, why have You forsaken Me?". However, if Jesus really did become sin for us, how is it that we still have a God who is truly holy? Similarly, how can Jesus suffer death and separation from God, when He is, himself, God? After all, God is immortal, yet Jesus clearly died.
1 Tim 1:17 (NASB)
Now to the King eternal, immortal, invisible, the only God, be honor and glory forever and ever. Amen.
Jesus Was Tempted
Since God is holy, we know that He cannot be tempted to sin.
James 1:13 (NASB)
Let no one say when he is tempted, “I am being tempted by God”; for God cannot be tempted by evil, and He Himself does not tempt anyone.
However, Jesus was tempted by Satan in the wilderness. We are told in the book of Hebrews that, at least in part, the purpose of His temptation was so that He, as our mediator and priest to God, can sympathize with our temptations.
Heb 2:18 (NASB)
For since He Himself was tempted in that which He has suffered, He is able to come to the aid of those who are tempted.
Heb 4:15 (NASB)
For we do not have a high priest who cannot sympathize with our weaknesses, but One who has been tempted in all things as we are, yet without sin.
If Jesus was tempted to sin, in all things, as we are, how can he be the Holy God?
Jesus Was Chosen by the Father
Of course, the very title of Messiah, or Christ means "The Anointed One", but there are also verses which speak of God choosing Jesus or appointing Jesus to His positions.
Acts 10:42 (NASB)
And He ordered us to preach to the people, and solemnly to testify that this is the One who has been appointed by God as Judge of the living and the dead.
Heb 1:2 (NASB)
In these last days has spoken to us in His Son, whom He appointed heir of all things, through whom also He made the world.
It would seem odd that God would appoint Himself to a position that he already occupied and that he would anoint Himself for representing Himself to the world. At the very least, it's a strange way to put it, if the goal is to be clear and to avoid misleading people.
Jesus Was Begotten
Everyone knows the following familiar verse:
John 3:16 (NASB)
For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life.
That is not the only verse which says that Jesus is begotten, however. For instance:
John 1:18 (NASB)
No one has seen God at any time; the only begotten God who is in the bosom of the Father, He has explained Him.
Heb 5:5 (NASB)
So also Christ did not glorify Himself so as to become a high priest, but He who said to Him, “You are My Son, today I have begotten You”
Non-trinitarians will commonly link these verses ones which call Jesus the firstborn.
Col 1:15 (NASB)
He is the image of the invisible God, the firstborn of all creation.
Rom 8:29 (NASB)
For those whom He foreknew, He also predestined to become conformed to the image of His Son, so that He would be the firstborn among many brethren
See also Rev 1:4-6.
The words "begotten" and "firstborn" clearly have connotations that Jesus was created and had a beginning. The fact that He was the "only" begotten certainly means that His beginning was very different from the rest of us, but to deny that He had a beginning certainly requires some mincing of words.
No One Has Seen God
Clearly, there were many witnesses who met, knew, and touched Jesus, but the Bible is clear that no one has ever seen God. It would be a strange claim to make if Jesus was indeed God.
1 Tim 6:13-16 (NASB)
I charge you in the presence of God, who gives life to all things, and of Christ Jesus, who testified the good confession before Pontius Pilate, that you keep the commandment without stain or reproach until the appearing of our Lord Jesus Christ, which He will bring about at the proper time—He who is the blessed and only Sovereign, the King of kings and Lord of lords, who alone possesses immortality and dwells in unapproachable light, whom no man has seen or can see. To Him be honor and eternal dominion! Amen.
See also 1 John 4:12.
Similarly, there are verses, such as 1 Tim 1:17 which say that God is invisible, further cementing the concept.
Jesus is Our Mediator
The Bible makes it clear that Jesus is our mediator. He is our High Priest who intercedes on our behalf.
1 Tim 2:5-6 (NASB)
For there is one God, and one mediator also between God and men, the man Christ Jesus, who gave Himself as a ransom for all, the testimony given at the proper time.
Rom 8:34 (NASB)
who is the one who condemns? Christ Jesus is He who died, yes, rather who was raised, who is at the right hand of God, who also intercedes for us.
Heb 6:20 (NASB)
where Jesus has entered as a forerunner for us, having become a high priest forever according to the order of Melchizedek.
If Jesus is God, how can he be a mediator between God and men? How can he intercede God on our behalf if he is, himself, God?
Conclusion
There are certainly other verses which add support to all of those various lines of reasoning. I'm also sure that there are other scriptural arguments which can be made against the doctrine of the Trinity. This is not an exhaustive list. It would take volumes to describe all of the various ways in which this doctrine has been debated over the millenia. I hope, however, that this sampling gives you a good enough idea of some of the key points and verses that can and have been used in the debate.
I am in no way implying that Trinitarians do not have good answers to all of these points. They do have answers to all of these questions that I raised. There are several other pages on this site where those kinds of questions have already been answered from the orthodox perspective.