A few additional (!) 
thoughts along the thread JA and I have been traveling:
The abstraction of mathematics itself points to a metaphysical quality. Derb has more or less acknowledged this by pointing out that his status as a Mysterion, as opposed to an atheist, is in part based upon the idea that mathematics and other principles, while corresponding to reality, appear to exist apart from specific reality. (I’m paraphrasing, but hopefully not far afield from the original idea.)
My earlier reference to the abstract quality of mathematics echos this very point – albeit backhandedly, given that I was on about the nature of “precision.” I think it’s fair to point out that what we often think of as material precision just as often relies upon certain abstractions. That these abstractions correspond to the material world doesn’t make them material in and of itself – and this is what I was trying to get at in regards to the metaphysical aspects of law and being.
The notion that metaphysical truths cannot be gotten at then is based on the practice of cordoning off metaphysics right around the area of incomprehensibility. This brings us right back to the essentials – the assumption of physicality or material existence upon all that we consider to be “precisely” known is a stolen base, one that all too many steal in trying to assert the superiority of scientific method as a basis for broader assertions.
This certainly brings out paradoxes in JA’s posts as well, which stemed from assertions about faith grounded in science. Faith in what? In the material things that science can get at? Not so much faith as the directly observable there. Faith in the broader metaphysical conclusions? JA contends that no one can get there. This leaves the assertion of no metaphysical reality as the default position, but just as atheism is in a sense a religious perspective (in the fundamental sense of religion as ideas about God, as opposed to the idea of religion as directed practice of those ideas towards God) the concept that there is no metaphysical reality is itself a metaphysical question. The answer therein is also metaphysical, and let there be no confusion about metaphysics as an area of philosophical inquiry and the broader idea of metaphysics (or metaphysical) as the domain outside the material physical world. In the case of that particular question, they overlap.
So the idea that metaphysical truths cannot be gotten at is posited itself as a metaphysical truth – which is much along the lines of the nonfoundationalist paradox regarding metanarratives (that the proposition that there are no encompassing metanarratives that explain reality is itself a metanarrative).
This then tends to be a self-defeating assertion.
