Part I: Definition and Historical Background, Relying On Others To Decide What We Should Believe
You Are Here Part II - Plurality in The Godhead
Part III - The Deity of Christ & The Deity of The Holy Spirit
Part IV: Passages That Supposedly "Prove" the Trinity.
Part V: The Grammar... Can it legitimately be used to support the idea that the Holy Spirit is the third Person of the Trinity
Part VI: The Holy Spirit... a Separate Person, Or The Divine Presence And Power Of The Father Himself
Part VII: The doctrine of the trinity that has remained virtually unchanged to this day found its roots in paganism not the Bible. This largely due to the part played by the Cappadocian Fathers - three ancient Greek philosophers and mystics.
Part VIII: The Son is "begotten" of the Father, and the Spirit "proceeds" from the Father. A difference yes, but not what The Cappadocian Fathers made it out to be
Part IX: Summary and Conclusion
ON THIS PAGE
Plurality in The Godhead
The Deity of Christ & The Deity of The Holy Spirit
Plurality in The Godhead
I'd like to remind the reader of some of what Dr. Bruce Metzger's said (All Emphasis Added)
"Because the Trinity is such an important part of later Christian doctrine, it is striking that the term does not appear in the New Testament. Likewise, the developed concept of three coequal partners in the Godhead found in later creedal formulations cannot be clearly detected within the confines of the canon. 
"Three coequal partners" cannot be found in the canon simply because there is no such thing. However, the Hebrew Scriptures very definitely point to more than one Person in the Godhead.
When referring to Yahweh, the singular form elôahh was used some 40 times in the Old Testament,
Behold, how happy is the man whom God (Heb. elôahh) reproves, So do not despise the discipline of the Almighty. (Job 5:17 NASB)
Tremble, O earth, before the Lord, Before the God (Heb. elôahh) of Jacob, (Psalms 114:7 NASB)
However, the plural elôhîym was used well over 2000 times.
If God is numerically singular, then one has to wonder why the Old Testament authors not only used a plural noun, but did so many more times than they used the singular.
The opening verse of the Bible says "In the beginning God (Heb. elôhîym) created the heavens and the earth".
Elôhîym is plural noun used in several places to refer to false gods. For example
You shall have no other gods (Heb. elôhîym) before Me. (Exodus 20:3 NASB)
Beware that your hearts are not deceived, and that you do not turn away and serve other gods (Heb. elôhîym) and worship them. (Deuteronomy 11:16 NASB)
Which means the verbs and pronouns used with Elohim should be in the plural but interestingly, when Elohim refers to the Lord God the verbs and pronouns are in the singular. 
Even more tellingly, when God spoke of himself He often used the plural pronoun. In the first example, the "our image" and "our likeness", cannot refer to angels since the very next verse makes it clear that man is made in the image of God Himself. (Emphasis Added)
Then God said, "Let Us make (Heb. na·‘a·seh) man in Our image, according to Our likeness .... God (Heb. elôhîym) created man in His own image, in the image of God (Heb. elôhîym) He created him; male and female He created them". (Genesis 1:26, 27 NASB)
Exactly the same form of the verb is used in Exodus 19:8
All the people answered together and said, "All that the LORD has spoken we will (Heb. na·‘a·seh) do!" And Moses brought back the words of the people to the LORD. (Exodus 19:8 NASB)
Similarly, Genesis 11:7 says (I cannot reproduce the exact Greek lettering)
"Come, let Us go down (Heb. nê·re·gah ) and there confuse their language, so that they will not understand one another's speech." (Genesis 11:7 NASB)
This form was also used in 1 Samuel 14:36
Then Saul said, "Let us go down (Heb. nê·re·gah ) after the Philistines by night and take spoil among them until the morning light, and let us not leave a man of them"... (1 Samuel 14:36 NASB)
Other examples include
Then the Lord God said, "Behold, the man has become like one of Us, (Heb. minnêy - a part of) knowing good and evil; and now, he might stretch out his hand, and take also from the tree of life, and eat, and live forever"-- (Genesis 3:22 NASB)
Then I heard the voice of the Lord, saying, "Whom shall I send, and who will go for Us?" Then I said, "Here am I. Send me!" (Isaiah 6:8 NASB)
Note: Most trinitarians read the "our" and "us" as reference to the persons of the Trinity, and the conversation in Genesis 11:7 as taking place between the persons of the Trinity. On the other hand, many non-trinitarians read the "our" and "us" as being a form of speech that uses the plural to emphasize the majesty of God. Some also consider the conversation in Genesis 11:7 being between God and His angels
However, neither explanation accounts for the fact that...
The Words Elôhîym and Yahweh are Applied To Two Different Beings
On more than one occasion the words elôhîym and Yahweh are applied to two different Persons in the same verse. For example, Genesis 19:24 very clearly speaks about more than one Yahweh... One rains fire and brimstone from the Other who is in Heaven.
Then the Lord (Heb. Yahweh) rained on Sodom and Gomorrah brimstone and fire from the Lord (Heb. Yahweh) out of heaven, (Genesis 19:24 NASB)
As commentator Adam Clark wrote most people take this verse as implying that although the brimstone and fire was from Yahweh the Father, it was Yahweh the Son who rained it down on Sodom and Gomorrah
Verse 8 of Zechariah 2 makes it clear that Lord (Heb. Yahweh) is speaking yet, in the next verse, He says Yahweh sent Him.
(8) For thus says the Lord (Heb. Yahweh) of hosts, "After glory He has sent me against the nations which plunder you, for he who touches you, touches the apple of His eye. (9) "For behold, I will wave My hand over them so that they will be plunder for their slaves. Then you will know that the Lord (Heb. Yahweh) of hosts has sent Me.
The case for plurality in the Godhead is made even stronger by the fact that in verse 12 of Isaiah 48, the speaker is obviously God, since He refers to Himself as the one who founded the heavens and the earth. In verse 15, the same speaker refers to Himself using the pronouns "I" and "Me" then in verse 16 distinguishes Himself from the Lord God (Yahweh) and from the Spirit of God.
(12) "Listen to Me, O Jacob, even Israel whom I called; I am He, I am the first, I am also the last. (13) "Surely My hand founded the earth, And My right hand spread out the heavens; When I call to them, they stand together. (14) "Assemble, all of you, and listen! Who among them has declared these things? The Lord loves him; he will carry out His good pleasure on Babylon, And His arm will be against the Chaldeans. (15) "I, even I, have spoken; indeed I have called him, I have brought him, and He will make his ways successful. (16) "Come near to Me, listen to this: From the first I have not spoken in secret, From the time it took place, I was there. And now the Lord (Heb. adônây) God (Heb. Yahweh) has sent Me, and His Spirit (Heb. rûach)." (Isaiah 48:12-16 NASB)
(To make it simpler, just read verses 12 and 16 together.
Listen to Me, O Jacob, even Israel whom I called; I am He, I am the first, I am also the last.... "Come near to Me, listen to this: From the first I have not spoken in secret, From the time it took place, I was there. And now the Lord (Heb. adônây) God (Heb. Yahweh) has sent Me, and His Spirit (Heb. rûach)."
But what about the verses that so explicitly state that ...
God is "One"
There are several verses in both the Old and New Testaments, that categorically state that God is One (largely why the Jews reject Jesus as God). However, since one of the earliest and most explicit of these declarations was made in the Old Testament, it is to the Hebrew that we should first turn.
The Shema Yisrael (Hear, Israel) is probably the best known prayer in Judaism, recited twice daily. Special emphasis is given to the first six words of the passage - which were spoken by Moses when he summoned all Israel and instructed them to carefully hear and learn all the statutes and the ordinances of the Lord so that they might live and prolong their days in the land of Canaan.
"Hear, O Israel! The Lord is our God, the Lord is one (Heb. echâd)! (Deuteronomy 6:4)
Malachi expressed a similar thought
"Do we not all have one (Heb. echâd) father? Has not one (Heb. echâd) God created us? Why do we deal treacherously each against his brother so as to profane the covenant of our fathers? (Malachi 2:10 NASB)
Deuteronomy 6:4 (the Shema) can be understood in different ways.
1) Moses was warning the nation that God was to be first priority:
Considering the circumstances - the eve of the invasion of Canaan, a nation steeped in idolatry and the worship of a pantheon of different gods - it is quite feasible that Moses was warning the Israelites that God was to be first priority. He was to be number one. This is supported by his very next words...
"You shall love the Lord your God with all your heart and with all your soul and with all your might. (Deuteronomy 6:5 NASB)
2) Moses could simply have been speaking numerically,
which is the most usual understanding of the passage and exactly how a scribe understood Jesus' reply when he (the scribe) asked the Savior which was the foremost commandment...
(28) One of the scribes came and heard them arguing, and recognizing that He had answered them well, asked Him, "What commandment is the foremost of all?" (29) Jesus answered, "The foremost is, 'Hear, O Israel! The Lord our God is One (Gk. heis) Lord; (30) And you shall love the Lord your god with all your heart, and with all your soul, and with all your mind, and with all your strength.' (31) "The second is this, 'you shall love your neighbor as yourself.' There is no other commandment greater than these." (32) The scribe said to Him, "Right, Teacher; You have truly stated that He is One, and there is no one else besides Him; (Mark 12:28-32 NASB)
Note: The Hebrew word yâchîyd (sole) would perhaps have been more appropriate if Moses had intended to teach God's absolute oneness. Genesis 22:2 below as an example of how yâchîyd was used,
He said, "Take now your son, your only (Heb. yâchîyd) son, whom you love, Isaac, and go to the land of Moriah, and offer him there as a burnt offering on one of the mountains of which I will tell you." (Genesis 22:2 NASB)
However, since the Bible tells us that Jesus, the Son of God, is also God (John 1:1, Hebrews 1:8 etc.) there can be no argument that there is a plurality in the Godhead.
But how is that possible?
"One" (echâd) Can Be A Collective Unit
English words tend to be very precise. However, in Biblical Hebrew a word can have more than one meaning, which often makes the exact meaning of many words best determined by the context.
In this case, the Hebrew word translated "one" is the Hebrew echâd which is used many, many times in the Old Testament, and usually means one. However, echâd (properly united) which comes from the root word âchad, which means to unify. In other words, echâd does not necessarily mean a single unit, but is also used to refer to collective nouns, as in the following examples...
And he made fifty taches of gold, and coupled the curtains one unto another with the taches: so it became one (Heb. echâd) tabernacle. (Exodus 36:13 KJV)
He took a yoke of oxen and cut them in pieces, and sent them throughout the territory of Israel by the hand of messengers, saying, "Whoever does not come out after Saul and after Samuel, so shall it be done to his oxen." Then the dread of the Lord fell on the people, and they came out as one (Heb. echâd) man. (1 Samuel 11:7 NASB)
And the raiders came from the camp of the Philistines in three companies: one (Heb. echâd) company turned toward Ophrah, to the land of Shual, (1 Samuel 13:17 NASB)
"However, I will not tear away all the kingdom, but I will give one (Heb. echâd) tribe to your son for the sake of My servant David and for the sake of Jerusalem which I have chosen." (1 Kings 11:13 NASB)
And the messenger that was gone to call Micaiah spake unto him, saying, Behold now, the words of the prophets declare good unto the king with one (Heb. echâd) mouth: let thy word, I pray thee, be like the word of one of them, and speak that which is good. (1 Kings 22:13 KJV)
Unsurprisingly, in several instances, one form of the word echâd carries the meaning of more than one person or thing united in a group or relationship. At the time of creation, one (ehad) day was comprised of morning and evening.
God called the light day, and the darkness He called night. And there was evening and there was morning, one (Heb. ehad) day. (Genesis 1:5 NASB)
The groups of people in the following examples remained individuals, yet became one as a group through their unity of purpose, belief etc.
The Lord came down to see the city and the tower which the sons of men had built. The Lord said, "Behold, they are one (Heb. ehad) people, and they all have the same language. And this is what they began to do, and now nothing which they purpose to do will be impossible for them. (Genesis 11:5-6 NASB)
Only on this condition will the men consent to us to live with us, to become one ((Heb. ehad) people: that every male among us be circumcised as they are circumcised. (Genesis 34:22 NASB)
And all the people gathered themselves together as one (Heb. ehad) man into the street that was before the water gate; and they spake unto Ezra the scribe to bring the book of the law of Moses, which the Lord had commanded to Israel. (Nehemiah 8:1 KJV)
The whole assembly together (Heb. ke-e-had) was 42,360, (Nehemiah 7:66 NASB)
The man said, "This is now bone of my bones, and flesh of my flesh; She shall be called Woman, Because she was taken out of Man." For this reason a man shall leave his father and his mother, and be joined to his wife; and they shall become one (Heb. ehad) flesh. (Genesis 2:23-24 NASB)
Simply put, Moses' use of the word echâd does not exclude a plurality in the Godhead. Nor, as you will see, does the Greek equivalent heis.
Heis, which Jesus used in place of the Hebrew echâd when He quoted Deuteronomy 6:4, is used several times in the New Testament to express God being "one"
yet for us there is but one (Gk. heis) God, the Father, from whom are all things and we exist for Him; and one (Gk. heis) Lord, Jesus Christ, by whom are all things, and we exist through Him. (1 Corinthians 8:6 NASB)
one (Gk. heis) God and Father of all who is over all and through all and in all. (Ephesians 4:6 NASB)
For there is one (Gk. heis) God, and one (Gk. heis) mediator also between God and men, the man Christ Jesus, (1 Timothy 2:5 NASB)
You believe that God is one (Gk. heis). You do well; the demons also believe, and shudder. (James 2:19 NASB)
However, like the Hebrew echâd, the Greek heis is also used for group unity, as well as equality.
When Jesus quoted Genesis 2:23-24 to express group unity, He used heis
and said, 'for this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one (Gk. heis) flesh'? "So they are no longer two, but one (Gk. heis) flesh. What therefore God has joined together, let no man separate." (Matthew 19:5-6 NASB)
Similarly, no one physically merges with a prostitute, nor can anyone who joins himself to the Lord be physically one with Him.
Or do you not know that the one who joins himself to a prostitute is one (Gk. heis) body with her? For He says, "the two shall become one (Gk. heis) flesh. But the one who joins himself to the Lord is one (Gk. heis) spirit with Him. (1 Corinthians 6:16-17 NASB)
In speaking of His and the Father's relationship, Jesus said He and the Father were one (Gk. heis)" (John 10:30), which was not only expressing His oneness with the Father but, from the reaction of the Jews who took up stones to punish him for blasphemy, was also unquestionably a declaration of His equality with God.
Jesus answered them, "I showed you many good works from the Father; for which of them are you stoning Me?" The Jews answered Him, "For a good work we do not stone You, but for blasphemy; and because You, being a man, make Yourself out to be God." (John 10:32-33 NASB)
Jesus also used the word heis when He prayed that His followers would all be one (united), just as He and the Father were one. In this case "one" cannot mean equality, but has to mean a unity of mind and purpose
that they may all be one (Gk. heis); even as You, Father, are in Me and I in You, that they also may be in Us, so that the world may believe that You sent Me. "The glory which You have given Me I have given to them, that they may be one (Gk. heis), just as We are one (Gk. heis); I in them and You in Me, that they may be perfected in unity (Gk. heis), so that the world may know that You sent Me, and loved them, even as You have loved Me. (John 17:21-23 NASB)
Continue On To Part III - The Deity of Christ and The Deity of The Holy Spirit. Challenging the doctrine of the Trinity does not mean challenging the Divinity of Christ and it does not mean challenging the Divinity of the Holy Spirit. The New Testament abounds with much proof of the deity of Jesus Christ, and Acts 5:3-4 is more than enough to clinch the issue of the Holy Spirit being God. HERE
 The Oxford Companion to the Bible. Editors Bruce M. Metzger and Michael David Coogan. Oxford University Press, USA; First Edition edition (October 14, 1993 Pg 782
 David Guzik's Commentary on Genesis 1. https://www.blueletterbible.org/Comm/guzik_david/StudyGuide2017-Gen/Gen-1.cfm