My conception of reason is based on determining what is true, completely and entirely irrespective of pragmatism. To call skeptical arguments irrational and call an anti-skeptical case rational would mean losing sight of the important fact that ONLY pragmatic considerations lead to the rejection of skepticism.
Rationality, to me, is defined as the hypothetical set of rules which reliably determine truth, not by coincidence, but because they must determine truth by their nature. Anything which does not follow said rules are irrational. Even if skepticism is false, believing in the world is irrational for me (and you, based on what I've heard from you and my definition) because nothing necessarily leads to a correlation between the senses and reality.
One of the rules of my rationality is that pragmatic considerations are not to be taken into account, as what is useful to believe and what is true have no necessary correlation. This applies for anything which has no necessary correlation with what is true.
What you're talking about is pragmatic, not rational. It is important to be aware of the distinction between what one may 'believe' for some reason and what is likely to be actually true, completely independent of such beliefs.
what is useful to believe and what is true have no necessary correlation
You seem to be referring to the distinction between instrumental and epistemic rationality. Yes, they are different things. The case I am trying to make does not depend on a conflation of the two, and works just fine if we confine ourselves to epistemic rationality, as I will attempt to show below.
OK, so I think your labeling system, which is clearly different from the one to which I am accustomed, looks like this:
...rationality = a set of rules which reliably and necessarily determi
I've raised arguments for philosophical scepticism before, which have mostly been argued against in a Popper-esque manner of arguing that even if we don't know anything with certainty, we can have legitimate knowledge on probabilities.
The problem with this, however, is how you answer a sceptic about the notion of probability having a correlation with reality. Probability depends upon axioms of probability- how are said axioms to be justified? It can't be by definition, or it has no correlation to reality.