Kadaveri, what you have posted is still a misunderstanding of the Trinity. For one thing, I don’t know of any place where the Qur’an refers to Allah as “the Father”. I’m sorry, but if you reject the Trinity by which the Father is invoked, then you cannot turn around and claim the Father whenever it suits you. Your own Qur’an rejects this idea of God as Father when it claims that He cannot have a son because He has had no consort! (6:101)
So which is it? Is Allah “the Father”, or is your own Qur’an lying?
And the nature of the Holy Trinity is such that it is not enough to just say that the Father, the Son, and the Holy Spirit are “united”. While this is true, they are also eternally uncreated and indivisible from one another. You cannot isolate one and say “aha! There is one god, and over there is the Son who is another god, and over there is the Holy Spirit who is another god”. It does not work that way. In the Nicene Creed, we affirm the Trinity in the following fashion:
We believe in one God,
the Father, the Almighty,
maker of heaven and earth,
of all that is, seen and unseen.
We believe in one Lord, Jesus Christ,
the only Son of God,
eternally begotten of the Father,
God from God, light from light,
true God from true God,
begotten, not made,
of one Being with the Father;
through him all things were made.
For us and for our salvation
he came down from heaven,
was incarnate of the Holy Spirit and the Virgin Mary
and became truly human.
For our sake he was crucified under Pontius Pilate;
he suffered death and was buried.
On the third day he rose again
in accordance with the Scriptures;
he ascended into heaven
and is seated at the right hand of the Father.
He will come again in glory to judge the living and the dead,
and his kingdom will have no end.
We believe in the Holy Spirit, the Lord, the giver of life,
who proceeds from the Father,
who with the Father and the Son is worshiped and glorified,
who has spoken through the prophets.
Nowhere in this bedrock of our faith is it said that the Son is a different
God than the Father. Indeed, He is eternally begotten of the Father! There was never a time when He was not, as He and the Father are “of one being”. The problem that Muslims have is with the incarnation, because there was a time when he had not yet been
incarnated - he had not yet been born of the Blessed Virgin. That does not mean that did not exist anymore than a Muslim should claim that Allah did not exist until Muhammad began receiving the Qur’anic revelations. Things most certainly can and do exist even when we cannot see them or perceive them, and this is true of nothing more than it is true of God.
The Holy Spirit proceeds from the Father (procession issues notwithstanding!). It only makes sense to say that the Holy Spirit is a “different” God if you want to argue that the Father is without holiness or without spirit. This is not wise. If we reduce God to the level of abstraction that Islam does, we lose what makes the Christian relationship with God different than that of other religions. Our God is not without Holiness, for He is Holiness itself and the source of all holiness (just as He is the source of the Holy Spirit, no matter what church you belong to!). Our God is not spiritless, because His Holy Spirit is what has spoken through the prophets. Again, Islam cannot deny this idea unless you want to open up the issue of exactly who or what was speaking through the angel Gabriel as he supposedly gave revelations of the Qur’an to Muhammad, or for that matter on what authority Muhammad pronounced anything. Not to mention that since Islam technically takes past (pre-Islamic) prophets for its own, it is extremely unwise to then rob God of His faculty to have spoken through other prophets, too, by denying the Holy Spirit.