Part I - Historical Background. Is the orthodox version of one God in three persons an unassailable and inviolable doctrine straight from the pages of Scripture? Not exactly! This incomprehensible doctrine was formally adopted in 381 AD as a defense against charges that Christians worshipped more than one God. It prevailed because it satisfied a number of requirements and gave the church a nice tidy solution. Yet, although unknown to the Scriptures, it somehow evolved into a litmus test for true faith.
Part II - ‘Proof Texts’. Passages that supposedly "prove" the trinity.
You Are Here Part III - The Grammar. Can the grammar legitimately be used to support the idea that the Holy Spirit is the third Person of the Trinity?
Part IV - The Deity of Christ and the Holy Spirit. The Bible very clearly shows that Christ is God AND ascribes Divinity to the Holy Spirit which leads to the question...
Part V - Can God be more than one?
Part VI - What is The Holy Spirit? - A separate person, or the Divine presence and power of the Father Himself?
Part VII - The Cappadocian Fathers. 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 - Begotten Vs. Proceeds. The Son is "begotten" of the Father and the Spirit "proceeds" from the Father. Different? Certainly! But not what The Cappadocian Fathers made it out to be
Part IX - Summary and Conclusion
ON THIS PAGE
Basic Rules That Govern Greek Nouns and Pronouns
Relative Pronouns Used To Indicate The Holy Spirit is a Person (but do they?)
The Greek Word ho
The Greek Word to
Demonstrative Pronouns Used To Indicate The Holy Spirit is Male (but do they?)
John 16:7-8 - Parakletos
Other Arbitrary and Undependable Translations
Basic Rules That Govern Greek Nouns and Pronouns
In English, the neuter gender (it) refers chiefly to inanimate objects that are neither masculine nor feminine. However, this is not the case in several other languages including French, Spanish, German and Greek in which the grammatical gender of nouns is not always linked to the actual gender. This often has English speakers scratching their heads.
Mark 1:9-10 is a classic example of what seems to be the arbitrary assignment of genders in Greek. In this verse Galilee is feminine, Jordan is masculine, water and Spirit are neuter, heavens is masculine, and dove is feminine.
In those days Jesus came from Nazareth in Galilee (F) and was baptized by John in the Jordan (M). Immediately coming up out of the water (N), He saw the heavens (M) opening, and the Spirit (N) like a dove (F) descending upon Him; (Mark 1:9-10 NASB)
Because Greek assigns a specific gender to every noun including inanimate objects, Greek grammar requires that all pronouns reflect the number and gender of the noun they stand in for. Simply put, pronouns have to agree with the grammatical gender that do not necessarily correlate with real life gender. In other words one cannot tell the gender of the noun from the pronoun. For example, the pronoun 'she' may not refer to a female
However, when translating Greek into English, one also has to know what the the gender and number of the noun is in English. In a basic lesson on Greek grammar, the site ibiblio says the following (Emphasis Addded)
In Greek, it would be quite normal to say something like, "the light shines in the darkness, and she has not overcome it"; because darkness is feminine and light is neuter, "she" would have to refer to the darkness, and "it" would have to refer to the light. Naturally, we wouldn't want to use "she" and "it" in an English translation of this sentence! 
In other words, we would use "it" if we know (or assume) the object is inanimate, "he" if we know (or assume) the object is male, and "she" if we know (or assume) it is female.
Similarly, in Hebrew, Pronouns Do Not Prove Gender
When the Bible says, for instance, "In the beginning God created the heavens and the earth" (Genesis 1:1), the Hebrew word for God is elôhîym, used well over two thousand times in the Old Testament. What is important to this topic is that both elôhîym and the singular form elôahh are masculine nouns.
Although God transcends gender the rules of grammar dictate that any pronoun used must agree in gender with the noun to which it is referring. In other word, just because the pronoun "He" is used of God, it does not necessarily mean that God is masculine but that the original word elôhîym is masculine.
Although God's Spirit is clearly not female, the word ruach (literally "breath" or "wind") translated "spirit" is a feminine noun.
The earth was formless and void, and darkness was over the surface of the deep, and the Spirit (Heb. ruach) of God (Heb. elôhîym)was moving over the surface of the waters. (Genesis 1:2 NASB)
It is hardly likely that God can be masculine and His Spirit feminine. But let's return to the Greek in the New Testament.
Relative Pronouns Used To Indicate The Holy Spirit is a Person
The Greek Word ho
The English words who or whom are relative pronouns used only to refer to living beings. In the following passages who or whom used for God the Father, Jesus, and people have all been translated from the Greek word ho.
God: My Father, who (Gk. ho. Strong's 3739) has given them to Me, is greater than all; and no one is able to snatch them out of the Father's hand. (John 10:29 NASB) [Source]
Jesus: and behold, a voice out of the heavens said, "This is My beloved Son, in whom (Gk. ho. Strong's 3739) I am well-pleased." (Matthew 3:17 NASB) [Source]
People: For this you know with certainty, that no immoral or impure person or covetous man, who (Gk. ho) is an idolater, has an inheritance in the kingdom of Christ and God. (Ephesians 5:5 NASB) [Source]
Ho is also used for the Holy Spirit.
But the Helper, the Holy Spirit, whom (Gk. ho. Strong's G3739) the Father will send in My name, He (Gk. ekeinos) will teach you all things, and bring to your remembrance all that I said to you. (John 14:26 NASB) [Source]
In Him, you also, after listening to the message of truth, the gospel of your salvation--having also believed, you were sealed in Him with the Holy Spirit of promise, who (Gk. ho. Strong's G3739 ) is given as a pledge of our inheritance, with a view to the redemption of God's own possession, to the praise of His glory. (Ephesians 1:13-14 NASB) [Source]
However, in Strong's Hebrew and Greek lexicon, several forms of a word are grouped together under a common number. In this case three related Greek words hos he ho are found under Strong's number G3739. However, all three of these pronouns do not necessarily mean who or whom, but can also mean which, what, or that. If you go to any of the links provided in the above examples and mouse over the word ho you will see what I mean. However, here are some examples...
Offering: And Jesus *said to him, "See that you tell no one; but go, show yourself to the priest and present the offering that (Gk. ho) Moses commanded, as a testimony to them." (Matthew 8:4 NASB) [Source]
Concealed Things: Therefore do not fear them, for there is nothing concealed that (Gk. ho) will not be revealed, or hidden that (Gk. ho) will not be known. (Matthew 10:26 NASB) [Source]
Sin: Flee immorality. Every other sin that (Gk. ho) a man commits is outside the body, but the immoral man sins against his own body. (1 Corinthians 6:18 NASB) [Source]
The Gospel: according to the glorious gospel of the blessed God, with which (Gk. ho) I have been entrusted. (1 Timothy 1:11 NASB) [Source]
Sacrificial Blood: but into the second, only the high priest enters once a year, not without taking blood, which (Gk. ho) he offers for himself and for the sins of the people committed in ignorance. (Hebrews 9:7 NASB). [Source]
In other words, John 14:26 and Ephesians 1:13-14 (above) could legitimately be translated
But the Helper, the Holy Spirit, that (Gk. ho) G3739 the Father will send in My name, He (Gk. ekeinos) will teach you all things, and bring to your remembrance all that I said to you. (John 14:26)
In Him, you also, after listening to the message of truth, the gospel of your salvation--having also believed, you were sealed in Him with the Holy Spirit of promise, that (Gk. ho) is given as a pledge of our inheritance, with a view to the redemption of God's own possession, to the praise of His glory. (Ephesians 1:13-14)
And there are plenty more examples HERE
These verses and others like them were translated who or whom not based on grammar. Using who or whom was a choice made by the translators based on their belief that the Holy Spirit was a person
The Greek Word to
It is exactly the same case when it comes to the Greek word to (Strong's number G3588). When speaking about the Holy Spirit, the English translation of 1 Corinthians 2:12 reads,
Now we have received, not the spirit of the world, but the Spirit who (Gk. to) is from God, so that we may know the things freely given to us by God, (NASB)
Interestingly the KJV version reads "the spirit which is of God"
The Greek to has also been used when the text speaks of Jesus and various other people regardless of number
Jesus: But when he had considered this, behold, an angel of the Lord appeared to him in a dream, saying, "Joseph, son of David, do not be afraid to take Mary as your wife; for the Child who (Gk. to) has been conceived in her is of the Holy Spirit. (Matthew 1:20 NASB)
People: For if you were cut off from what is by nature a wild olive tree, and were grafted contrary to nature into a cultivated olive tree, how much more will these who (Gk. to) are the natural branches be grafted into their own olive tree? (Romans 11:24 NASB)
Get up, take the Child and His mother, and go into the land of Israel; for those (Gk. to) who sought the Child's life are dead." (Matthew 2:20 NASB)
However the word is also used for inanimate objects and abstract nouns.
Prophecy: Now all this took place to fulfill what (Gk. to) was spoken by the Lord through the prophet: (Matthew 1:22 NASB)
Salvation: For this reason I endure all things for the sake of those who are chosen, so that they also may obtain the salvation which (Gk. tes ) is in Christ Jesus and with it eternal glory. (2 Timothy 2:10 NASB)
Knowledge: Paul, a bond-servant of God and an apostle of Jesus Christ, for the faith of those chosen of God and the knowledge of the truth which (Gk. tes) is according to godliness, (Titus 1:1 NASB)
In other words, 1 Corinthians 2:12 could have legitimately been translated "the Holy Spirit, that (Gk. to) the Father will send in My name".
Once again, using who or whom was a choice made by the translators... a decision made based on what they already believed.
Demonstrative Pronouns Used To Indicate The Holy Spirit is Male
The site letusreason.org says
The Holy Spirit is identified as a Person by John, using in the Greek the masculine ekeinos in Jn. 16:13. 
This is not correct.
John 16:13 reads thus (Note: In this verse the pronoun 'He' has been used six times however, in the original Greek only the first "He" (in bold) exists. The others five were added to make the sentence flow in English.)
"But when He (Gr. ekeinos), the Spirit of truth, comes, He will guide you into all the truth; for He will not speak on His own initiative, but whatever He hears, He will speak; and He will disclose to you what is to come. (John 16:13 NASB)
He Will Guide: "He will guide" has been translated from the Greek word hodegesei which simply means "guide". This word has been sparingly used in the New Testament. In the following example, the Ethiopian eunuch was reading the book of Isaiah and told Philip he could not understand it "unless someone guides (Gk. hodegesei ) me". The form of the verb used is the third person singular which means the "someone" did not have to be male. Interestingly the Greek is said to be Masculine Singular but applies to anyone apparently regardless of gender. [Source]
And he said, "Well, how could I, unless someone (Gk. tis) guides (Gk. hodegesei) me?" And he invited Philip to come up and sit with him. (Acts 8:31 NASB)
He Will Speak: Similarly, the actual Greek reads "He will speak from himself" (speak on His own initiative in the English translation). The "himself" means absolutely nothing because heautou (the Greek word used) does not necessarily refer to a male person but is also used in other contexts.
"Then it goes and takes along with it seven other spirits more wicked than itself (Gk. heautou), and they go in and live there; and the last state of that man becomes worse than the first. That is the way it will also be with this evil generation." (Matthew 12:45 NASB)
Although the next two examples say "himself" Paul was obviously not speaking to men only.
But each one must examine his own work, and then he will have reason for boasting in regard to himself (Gk. heautou) alone, and not in regard to another. (Galatians 6:4 NASB
So then each one of us will give an account of himself (Gk. heautou) to God. (Romans 14:12 NASB)
But doesn't the first "He" in the original Greek count?
The Greek translated "He" (Strong's G1565) is a demonstrative pronoun i.e., a pronoun that points to a specific man, woman, thing (or things). However, as with all Greek verbs, there are several forms of the word under this particular number. The precise form used by John was ekeinos which is used some 240 times in the New Testament.
Strong's According to Strong's ekeinos means that one (or neut. that thing). 
blueletterbible: "The KJV translates Strong's G1565 in the following manner: that (99x), those (40x), he (40x), the same (20x), they (14x), miscellaneous (38x)." .
Although ekeinos usually refers to a person, it has also been occasionally used for inanimate objects as in the following examples.
A field: For this reason that (Gr. ekeinos) field has been called the Field of Blood to this day. (Matthew 27:8)
God's Word: He who rejects Me and does not receive My sayings, has one who judges him; the word I spoke is what (ekeinos) will judge him at the last day. (John 12:48 NASB) [Source]
In the following examples, ekeines is a different form of ekeinos. It is a feminine verb used because 'way' and 'city' are both feminine.
When He came to the other side into the country of the Gadarenes, two men who were demon-possessed met Him as they were coming out of the tombs. They were so extremely violent that no one could pass by that (Gk. ekeines) way. (Matthew 8:28 NASB)
And as for those who do not receive you, as you go out from that (Gk. ekeines) city, shake the dust off your feet as a testimony against them." (Luke 9:5 NASB)
Although they capitalized the word "One" and although grammatically correct, I would love to know why the NASB translates ekeinos into "that one” in reference to Christ in John 4:25,
The woman said to Him, "I know that Messiah is coming (He who is called Christ); when that One (Gk. ekeinos) comes, He will declare all things to us." (John 4:25 NASB)
Yet, in John 14:26, and 16:13, it translates ekeinos into "He" when referring to the Holy Spirit.
"But the Helper, the Holy Spirit, whom (Gk. ho) the Father will send in My name, He (Gk. ekeinos) will teach you all things, and bring to your remembrance all that I said to you. (John 14:26 NASB)
"But when He (Gk. ekeinos), the Spirit of truth, comes, He will guide you into all the truth; for He will not speak on His own initiative, but whatever He hears, He will speak; and He will disclose to you what is to come. (John 16:13 NASB)
The NASB reads
that is the Spirit of truth, whom (Gk. ho) the world cannot receive, because it does not see Him or know Him, but you know Him because He abides with you and will be in you. (John 14:17 NASB)
Note: the English word "he" (in bold above) is not in the original text, but added to simplify reading. According to the Interlinear Bible, John 14:17 reads
the spirit of truth whom the world is not able to receive because not it does see him (Gk. auto) nor know but you know him (Gk. auto) for with you he abides and in you he will be. [Source]
The word auto was used twice in this verse but does not necessarily mean him. This same form of the word is also used in Luke in reference to Jesus' body after His death and for inanimate objects.
this man went to Pilate and asked for the body of Jesus. And he took it (Gk. auto) down and wrapped it (Gk. auton) in a linen cloth, and laid Him in a tomb cut into the rock, where no one had ever lain. (Luke 23:52-53 NASB)
having canceled out the certificate of debt consisting of decrees against us, which was hostile to us; and He has taken it (Gk. auto) out of the way, having nailed it (Gk. auto) to the cross. (Colossians 2:14 NASB)
I took the little book out of the angel's hand and ate it (Gk. auto), and in my mouth it was sweet as honey; and when I had eaten it (Gk. auto), my stomach was made bitter. (Revelation 10:10 NASB) [Source]
In other words, the Greek pronoun auto did not necessarily have to be rendered "him" unless,of course, the gender of the Holy Spirit was pre-assumed. Also remember that there was no reason to translate ho into the English whom. This relative pronoun can also mean which, what, or that. See Strong's Number G3739 above.
John 16:7-8 - Parakletos
John records several instances when Jesus referred to the Holy Spirit as the parakletos, a word that has been translated advocate, comforter, helper etc. depending on which version of the Bible you read.
"But I tell you the truth, it is to your advantage that I go away; for if I do not go away, the Helper (Gk. parakletos) will not come to you; but if I go, I will send Him (Gk. auton) to you. And He, when He (Gk. ekeinos) comes, will convict the world concerning sin and righteousness and judgment" (John 16:7-8 NASB).
About this verse, the New Catholic Encyclopedia says
So clearly does St. John see in the Spirit a person who takes Christ's place in the Church, that he uses a masculine pronoun (Greek) in reference to the Spirit even though (spirit) is neuter in gender (16.8, 13-16). Consequently, it is evident that St. John thought of the Holy Spirit as a Person, who is distinct from the Father and the Son, and who, with the glorified Son and the Father, is present and active in the faithful (14.16; 15.26; 16.7). 
Which is quite untrue on more than one count.
Although the word Spirit (pneumatos) is masculine it is not used in this verse. Parakletos the subject of all three sentences is male. Even if John had used a masculine personal pronoun it was not necessarily because he was convinced that the Holy Spirit is the male third person of the Trinity, but because Greek grammar would require him to do so.
In any case, we cannot assume the pronouns John used were masculine. As previously mentioned, ekeinos has been used of inanimate objects (See Above). The Greek auton rendered "Him" in John 16:7-8 has also been used of a lamp in Matthew 5:15 and of the Gospel in Matthew 13:20
nor does anyone light a lamp and put it under a basket, but on the lamp stand, and it (Gk. auton) gives light to all who are in the house. (Matthew 5:15 NASB)
The one on whom seed was sown on the rocky places, this is the man who hears the word and immediately receives it (Gk. auton) with joy; (Matthew 13:20 NASB) [Source]
Other Arbitrary and Undependable Translations
What is interesting is the fact that, in some passages of the King James Version the translators, who certainly believed the Spirit to be the male third person of the Trinity, used neuter pronouns when referring to the Spirit...
The Spirit (Gk. pneuma) itself (Gk. autos) beareth witness with our spirit, that we are the children of God: (Romans 8:16 KJV)
Likewise the Spirit (Gk. pneuma) also helpeth our infirmities: for we know not what we should pray for as we ought: but the Spirit itself (Gk. hautou) maketh intercession for us with groanings which cannot be uttered. (Romans 8:26 KJV)
For it is not ye that speak, but the Spirit of your Father which (Gk. ho) speaketh in you. (Matthew 10:20 KJV)
Searching what, or what manner of time the Spirit of Christ which was in them did signify, when it testified beforehand the sufferings of Christ, and the glory that should follow. (1 Peter 1:11 KJV)
However, in the more modern NASB, these very same verses are translated with masculine the pronouns "he", "himself", or "who" which all indicate a person.
The Spirit (Gk. pneuma) Himself (Gk. autos) testifies with our spirit that we are children of God, (Romans 8:16 NASB)
In the same way the Spirit (Gk. pneuma) also helps our weakness; for we do not know how to pray as we should, but the Spirit Himself (Gk. hautou) intercedes for us with groanings too deep for words; (Romans 8:26 NASB)
"For it is not you who speak, but it is the Spirit (Gk. pneuma) of your Father who speaks in you. (Matthew 10:20 NASB)
seeking to know what person or time the Spirit (Gk. pneuma) of Christ within them was indicating as He predicted the sufferings of Christ and the glories to follow. (1 Peter 1:11 NASB)
Finally, note how the CLV (Concordant Literal Version) translates three verses from John. Not because the translators decided to de-emphasize the Holy Spirit as a person, but because Spirit (Greek pneuma) is neuter. (Emphasis Added)
the spirit of truth, which the world can not get, for it is not beholding it, neither is knowing it. Yet you know it, for it is remaining with you and will be in you. (John 14:17 CLV) 
Now the consoler, the holy spirit, which the Father will be sending in My name, that will be teaching you all, and reminding you of all that I said to you. (John 14:26 CLV) 
Yet whenever that may be coming - the spirit of truth -it will be guiding you into all the truth, for it will not be speaking from itself, but whatsoever it should be hearing will it be speaking, and of what is coming will it be informing you." (John 16:13 CLV) 
The message that comes across loud and clear is that there is no grammatical foundation for the orthodox view of the Holy Spirit
Doctrinal Bias Is Responsible For Referring To The Holy Spirit With Masculine Pronouns. So if the Holy Spirit is not the masculine 'Third Person' of the Trinity who or what is it?
Continue On To Part IV - 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 nor 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 show the Bible attributes Divinity to the Holy Spirit. HERE
 Pronouns and gender. http://www.ibiblio.org/koine/greek/lessons/pronoun.html. Note: ibiblio.org is a collaboration of the School of Information and Library Science, the School of Journalism and Mass Communication, and Information Technology Services at the University of North Carolina at Chapel Hill.
 Mike Oppenheimer. The Holy Spirit Is A Person. http://www.letusreason.org/Trin4.htm
 New Catholic Encyclopedia, 1965, Spirit of God, Vol 13, p574-576