I think you limit God by saying that he can't use his Holy Spirit to call people out of the World.
Dear Beans, if I said that I was wrong, and you are correct in my opinion in saying that the Holy Spirit is used in calling people out of the world and that would entail John 16:8. And when He is come, He will reprove the world of sin, and of righteousness, and of judgment. Not all respond.
How ever one would like to express it, the result is like that of Abraham; James 2:23, And the scripture was fulfilled which saith, Abraham believed God, and it was imputed unto him for righteousness. What were the magical words? I do not know if there is a given recipe from organized religion better than another as to how we come to the point of understanding, but I do know and feel the result of a life headed for hell like mine was that now has a hope and love of God.
To me, the moment we believe God, we for the first time see, we hear, and we understand through that measure of faith God has given us the hope we have in spiritual things. John 3:3 puts it this way: Except a man be born again, he cannot see the kingdom of God.
I reckon the following scriptures tell it as simple as any, and I know what the word "Believe" means to me. Over time God has produced fruit in my life as He works in me to will, and to do of His good pleasure. Were these things necessary to my salvation? No; they are the product of it. We are God's workmanship and that molding unto the image of His Son will continue until we are face to face with our Savior one glad day.
Acts 16:31 And they said, Believe on the Lord Jesus Christ, and thou shalt be saved . .
Romans 10:9 That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.
My thoughts.