I've spent years pondering the question you asked and I have to tell you, there is only ONE question worth asking on which
everything (EVERYTHING) stands or falls. It is the prime foundational argument. It is the basis on which all of the Jehovah's Witness
mumbo jumbo rests.
The question concerns : Source.
The source of all theology, doctrine, chronology, policy, conditions, admonition and counsel is THE BIBLE.
WHY, IF THE BIBLE IS THE INERRANT WORD OF GOD, have the original, hand-written (autograph manuscript) scriptures NOT BEEN PRESERVED?
Why do we only have (not copies, or copies of copies) 4th century snippets, fragments, tatters, pieces of so-called copies (of copies, of copies of copies) to go on to PROVE what we believe??
The majority of what exists in museums are generations removed from any pure, unedited, unexpurgated, un-tampered-with PROVABLE document.
In fact, what translations are based on are certain version of late generation revisions of revisions of revisions of hearsay FRAUDULENTLY presented to the public as IDENTICAL to originals!
Do you understand what I am saying?
IF GOD DID NOT SEE FIT TO PRESERVE SCRIPTURE (original, autograph, pure manuscript inspired originals) it must be FOR A REASON.
Think about it for a moment!
The Catholic Church was absolutely obsessive compulsive about finding and preserving every holy relic, artifact, shroud, knuckle bone, splinters from the "true cross", etc. of every holy person they could find.
WHY WOULD THEY NOT preserve the holiest of all documents on which mankind's true faith would rest too??
It boggles the mind!
You can't pretend GOD DID SEE FIT to preserve latter generation copies WHICH CONTRADICT other later generation copies and call it JUST AS GOOD.
This is what modern day christianity tries to pass off as sound reasoning!
Every church in Christendom that pretends the Bible is the inerrant word of God only goes so far as to assert the inerrancy is in THE ORIGINALS and not in the copies!!
All we have are those very copies which themselves have selectively been tampered with!
Why did the Watchtower see fit to translate THEIR OWN VERSION of the bible (New World Translation)?
For the SAME REASON every other denomination produced theirs!
Namely, to have a basis for their own proprietary INTERPRETATION to rest on something appearing to be divine!
It is bait and switch, pure and simple.
So,your question is this: HOW can you base your faith on "what the bible says" when we DON'T HAVE a pure, original bible in the first place?
Think how many doctrines of Jehovah's Witnesses hang on one word or phrase!!
We CAN'T POSSIBLY KNOW what the original word or phrase ACTUALLY WAS!
There is no way to check---to match against the original-----we only have hearsay!
How do you base a doctrine or theology that pretends to be THE ONLY TRUE RELIGION--on something that doesn't exist???
Do you see how important this is foundationally?
No PURE and exact scripture=No PURE and exact rendering or interpretation or inspiration.
It is an intellectual dead end to insist that the Bible we have today is JUST AS GOOD as the original without any possible way of comparing it with a pure autograph original kept in a museum.
What you have is the Watchtower Society claiming that false scriptures have been added throughout history (1 John 5:7 for example) for false religion to PROVE their false doctrines. Yes, this is true. BUT THIS PROVES THE BIBLE HAS NOT BEEN PRESERVED by God against tampering and impurity---doesn't it??
Yes!
False premise=False conclusion.
Getting Baptised into a religion that bases their beliefs on specific words, phrases (scriptural citations) and interpretations of exactitude WHEN THERE IS NO PURE COPY OF THOSE WORDS in existence is assinine, intellectually dishonest and fraudulent.
It will come down to willingness to be GULLIBLE. (i.e. they will call it "faith.")