Although the writings of the "Church Fathers" should not be allowed to interfere with clear and self-explanatory teachings from the Bible, in areas where interpretation is needed, such writings can help in establishing what early Christians believed. Late first century Christian writer Athenagoras reveals in what way the "Holy Spirit" was viewed:
"The Holy Spirit Himself also, which operates in the prophets, we assert to be an effluence of God, flowing from Him, and returning back again like a beam of the sun." - Athenagoras' A Plea For The Christians (Chapter 10)
"For, we acknowledge a God, and a Son his Logos, and a Holy Spirit, united in essence, - the Father, the Son, the Spirit, because the Son is the Intelligence, Reason, Wisdom of the Father, and the Spirit an effluence, as light from fire." - Athenagoras' A Plea For The Christians (Chapter 24)
While we could argue about what the word from which 'effluence' is translated means, it is clear from both short illustrations that Athenagoras understood the Holy Spirit to be a radiation from the Father. Light is a product of the sun and fire, but never the sun or fire itself.
Now, since I don't have the Greek manuscripts from which Athenagoras' writings have been translated, then I and other readers are a the mercy of Rev. B. P. Pratten who translated his work. So, for instance, when the Rev. translates from the Greek 'himself' (with reference to the Holy Spirit), there is no way of knowing if this is a legitimate translation. In fact, the Greek word for 'spirit' (Greek = 'pneuma') is a 'neuter' or 'it' word. So one wonders whether the Rev. has actually interpreted a neuter pronoun to mean 'himself'.
A similar situation exists with regard to the promised 'comforter' (Greek = 'parakletos') of John 14:15-17 and John 16:7-11. The 'gender' of the Greek word for 'comforter' (in some Bible versions called 'advocate') is masculine. That of course does not mean that the word cannot be applied to females. Koine Greek, along with modern languages like German, have three genders and in many cases words are given what appear to be - at least to many native English-speaking people - an arbitary gender. Just because a word has a masculine gender, that does not prove that it refers to a male person or even a person at all. For instance, the Hebrew word for earth ('arets') is 'feminine' by gender, and although a literal translation of Genesis 1:2 begins: "now-the-earth she-was formless" (Hebrew = "w'harets hay'thah chohuw"), this does not make the earth a female person. In the above cited scriptures from John, many English translations use the pronouns 'he' and 'him' with reference to the 'comforter', but as has been shown this is based upon a literal translation. At the end of the day, one's translation of this passage of Scripture will reflect one's existing view of who/what the 'Holy Spirit' is.
So an unbiased examination of the 'Holy Spirit' has got to be based on what the Scriptures tell us as a whole. The 'Holy Spirit' has been described as 'saying' things, but then again blood (which is not a person) has been said in Scripture to 'cry out'. Thus, there are arguments both ways with regard to such scriptures. However, the majority of references to the 'Holy Spirit' or 'God's Spirit' speak of 'it' as being 'distributed among', 'poured out on', and 'filling' people. so it is no wonder that many people come to the conclusion that the 'Holy Spirit' is an energising power of God rather than an actual person. This certainly fits Athenagoras' illustration of 'it' being like light that emanates from fire.
I should like to make a comment on the expression, "God is a mystery". This appears to be used by at least some trinitarians as a conversation stopper. It is also viewed by some who have contrary views - and I don't mean to offend anyone - as "a cop out". I think Tertullian's words directed to those who were trying to uphold their own view of God is quite apt. He said (and I'm paraphrasing here): "Then one can imagine God to be anything one wishes, on the basis that anything is possible with God". Again, with this train of thought, he says: "God could have made man with wings, but just because He could does not mean that he actually did." For many people the "God is a mystery" strategy holds no water whatsoever. In fact there seems to be a condescending aspect to it in that the problem is deemed to be with the questioner's comprehending the trinity, not with whether or not the trinity is well-founded on careful examination of Scripture. It should be noted that many of those who do not accept the trinity doctrine refuse to be psychologically bullied (e.g. "Well every Christian scholar I know believes it") into believing a doctrine that emerged out of an era when political expediency was more important than the true nature of 'God', his 'Son', and the 'Holy Spirit'.
I'm afraid I treat the established 'orthodox' churches and their doctrines with the same degree of sober examination as I did the WTS.