Is sanity rational?

[Mudhammam]

Certainly it's sane. But is it rational? Can arbitrary value judgments ever really be rational?

Yeah, I would say so. I think the rationale of a value judgment is how we often determine its worth, either to ourselves or how (in our view) it ought to be evaluated by others. I know you're no fan of pragmatism but here I think its method proves both invaluable and inevitable: Tacitly implied in questions of value is that the object of our discourse makes a practical difference to conscious experience (actually or hypothetically). This idea--that anything matters at all--may be to some degree arbitrary and not really subject to distinction of rational and irrational, but then as I already suggested, can't the same be applied to virtually everything? (Such as if I were to simply plug my ears and stick out my tongue, brandishing solipsism against anyone who ever tried to persuade me of anything counter-intuitive to my wishes or desires?)

I think if you're looking for an absolute principle to draw from, in order to persuade another, Ben, then no, you probably will not find that. However, that applies to both logic and morality as far as I can tell. There are certain rules and axioms that human beings cannot reduce any further without entering the absurd and self-refuting (or self-annihilating); it is from basic, internally consistent principles that all concepts and percepts are derived (in morality, it would be the Golden Rule or its inverse).