This can be very confusing. Let me clarify this. First, you need some basic Scientology concepts.
When Scientologists speak about knowing something, they are talking about what L. Ron Hubbard called "knowingness". Hubbard defined knowingness as "self-determined knowledge".
To say that more plainly, in Scientology, "knowingness" is what you "know" without any information, facts, evidence from outside yourself. It is what you, yourself, have decided is true.
You will note that this definition of "knowingness" would also be a perfect definition of belief.
This is not some trivial bit of Scientology, this is core Scientology dogma. This is tied to what Hubbard said about "OT" powers of "postulating". According to Hubbard, postulating is creating reality by just deciding that something exists or that something is in a certain state.
According to Hubbard, if you "postulate" something without any doubts or reservations, it must become true. This is what OT powers are all about.
And this is "knowingness". If you self-determinedly "know" something, and hold that "knowingness" without any doubts or reservations, then, according to Scientology, it will be true.
It's like telling people that, if they can hold a wish in their mind for an hour without ever thinking of pink elephants, that wish will come true.
Good luck with that.
But Scientologists believe this. And so they believe, pardon me, know that Scientology works, that everything the church says is true, that David Miscavige is the most wonderful person in the whole universe.
And they must hold this
And so you have someone who has attested to being "able to talk to anyone on any subject" -- and who obviously can't do that -- still "knowing" that Scientology works.
You have Clears -- who get sick -- who still "know" that Scientology works.
You have Scientologists, who can easily see the "OTs" around them struggling and failing in life -- still "knowing" that Scientology creates "true OTs".
Scientology true believers will put up with the most amazing abuse, broken promises, greed and fraud from the Church of Scientology -- and still "know" that the Church of Scientology is perfect and good.
Because when they say they "know" these things, it means they believe these things and they desperately hope that their belief will make it come true.
Scientology defines itself as "knowing how to know". Using the Scientology definition of "know", we can finally translate that: "Scientology: Learning how to believe".
And now you can understand what a Scientologist is actually saying when they say they "know Scientology works", and why they cannot tolerate any discussion or outside facts. They are trying not to think of pink elephants.