@markoos,
I tend to agree with Wittgenstein, Lyotard, and others.
Think about what verifiability means more broadly: it means that you
corroborate something (in this case a proposition) with evidence from a different source.
So if a metaphysical claim, even a convincing logical proof, has no reference at all outside of the human imagination, then how might we decide whether it's true, false, or at all meaningful?
Another way of phrasing the problem is to ask what we know about our own ability to reason and to think logically. In 2009, in an empirically verifiable way, we know that reasoning ability consists in our brain. And reasoning is dependent upon education, intelligence, age, and it is subject to all kinds of injuries and derangements from disease to drugs, etc.
In other words, our brains produce logic; and with the common denominator of language we share logic with one another. But there is no
necessary correspondance between logic and the world outside our brain. So if a metaphysical assertion exists only in logic, why should we ever assume that it's a function of reality and not just our imagination and creativity?