Well, that seems a funny way of phrasing things.
"has already taken place" makes it sound like believing is a one-time thing, "one and done".
It's present tense, not future, so they are already believing.
Further, the main aspect of the present tense is its continuous aspect. Believing is an ongoing thing, for the rest of our lives. As Dr. Plummer mentions, it's evidence of a regenerated heart.
In regards to the event of being born again believing is in reference to a one-time event (thing).
Once one is born again we are not in our natural condition, but have received life and the Spirit of God.
If I asked you, "Theo, are you still believing Jesus died for your sin," it would be a little bit silly, wouldn't it?
I can say that I believe far more now than I did when I was saved. For me, that Christ died on the Cross that men might be reconciled to God in an eternal context isn't open for discussion. It's just a fact.
My faith, though, is a different story, because my faith is the result of my belief.
This is why Atheists are so confused, because they do not think they have faith, lol.
So I would agree faith follows believing, because one has to have something to believe in before they can express faith in that belief. The Comforter is going to being conviction of sin to all unbelievers, but not all unbelievers will respond to the Ministry, and what would be debated is whether they "believed," or whether they rejected the truth.
Personally, I believe they do believe but intentionally reject the Gospel because of their own desires. For example, someone might reject the truth because they want to remain in the religion they were brought up in. Doesn't mean they don't believe Jesus died on the Cross in their place for their sins. And I am not saying dogmatically that they do believe, but that this is my own opinion.
For those who do yield to the Comforter's convicting ministry, they are born again.
We are told how men are saved:
Acts 16:29-31 King James Version
29 Then he called for a light, and sprang in, and came trembling, and fell down before Paul and Silas,
30 And brought them out, and said, Sirs, what must I do to be saved?
31 And they said, Believe on the Lord Jesus Christ, and thou shalt be saved, and thy house.
Look at the conversion of Cornelius. Again, we are told the progression, or order of salvation.
King James Version
13 And he shewed us how he had seen an angel in his house, which stood and said unto him, Send men to Joppa, and call for Simon, whose surname is Peter;
14 Who shall tell thee words, whereby thou and all thy house shall be saved.
15 And as I began to speak
, the Holy Ghost fell on them, as on us at the beginning
16 Then remembered I the word of the Lord
, how that he said, John indeed baptized with water; but ye shall be baptized with the Holy Ghost.
17 Forasmuch then as God gave them the like gift as he did unto us, who believed on the Lord Jesus Christ;
what was I, that I could withstand God?
18 When they heard these things, they held their peace, and glorified God, saying, Then hath God also to the Gentiles granted repentance unto life.
That Cornelius heard the Gospel was important enough for God to send them to Peter that they might hear the Gospel.
God gave the gift of Life to those who believed.
These are, according to Peter, the words by which Cornelius was saved. This is not the only place where the Gospel is intrinsic to salvation, and specifically the New Birth:
1 Peter 1:22-23 King James Version
22 Seeing ye have purified your souls in obeying the truth through the Spirit unto unfeigned love of the brethren, see that ye love one another with a pure heart fervently:
23 Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever.
James 1:18 King James Version
18 Of his own will begat he us with the word of truth, that we should be a kind of firstfruits of his creatures.
1 Peter 1:12 King James Version
12 Unto whom it was revealed, that not unto themselves, but unto us they did minister the things, which are now reported unto you by them that have preached the gospel unto you with the Holy Ghost sent down from heaven; which things the angels desire to look into.
So, to make a long story short (I know, too late), Regeneration is dependent on one receiving the Gospel and believing it.
And it is only through the Ministry of the Comforter that men have been able to understand the Mystery of Christ.
And this is what I believe that some of you are really
not going to like: no man was born again before Pentecost, because the Gospel was a Mystery not revealed in past Ages, generations, to any of the sons of men, but is now (in this Age) revealed to men by the Holy Ghost sent down from Heaven.