Yes, there are things that are unknowable, even with the tools of empiricism.
But pointing out this issue, in no way supports the idea of using a non-sense ideology in its place, or even ascribing any value to such a thing.
> that holds that there is value in both kinds of knowledge
No, there is no knowledge in mysticism. And is it a bad argument to point out a supposed problem in empiricism, as a justification for a different system, when that other system doesn't deal with the problem any better.
> believing something irrational to be true, makes it true.
Believing something to be true, does not make it true, unless you redefine the word "true" to a nonsense definition of "Well a true thing, is whatever we believe to be true. Gotcha, I win! I just created a self-consistent tautology, by playing word games, and making up a new definition! You can't call me wrong, because it's a consistent, self referential belief! That intro to philosophy class sure was useful!"
