There are all kinds of things that are true in every possible universe that aren’t self-evident. Look up “necessary a posteriori” for examples. So no, self-evident is not the same as necessary, at least not according to a very popular philosophical approach to possible worlds (Kripke’s). More generally, “necessity” is a metaphysical property, and “self-evidence” is an epistemic property. Just because a proposition has to be true does not mean it is going to be obvious to me that it has to be true. Even Descartes makes this distinction. He doesn’t regard all the truths of mathematics to be self-evident (he says he may be mistaken about their derivation), but presumably he does not disagree that they are necessarily true. (Come to think of it, he may disagree that they are necessarily true, given his extreme theological voluntarism, but that’s an orthogonal debate.)
As for your question about standards: I think it is a very plausible principle that “ought” implies “can”. If I (or anyone else) have an obligation to do something, then it must at least be possible for me to do it. So, in so far as I have a rational obligation to have justified beliefs, it must be possible for me to justify my beliefs. If you’re using the word “justification” in a way that renders it impossible for me to justify any belief, then I cannot have any obligation to justify my beliefs in that sense. And if that’s the case, then skepticism regarding that kind of justification has no bite. Sure, my beliefs aren’t justified in that rigorous sense, but if I have no rational obligation to justify them, why should I care?
So either you’re using “justification” in a sense that I should care about, in which case your standards for justification shouldn’t be so high as to render it impossible, or you’re using “justification” in Descartes’s highly rigorous sense, in which case I don’t see why I should be worried, since rationality cannot require that impossible standard of justification. Either way, I don’t see a skeptical problem.
It seems we’re using different definitions of words here. Maybe I should clarify a bit.
The definition of rationality I use (and I needed to think about this a bit) is a set of rules that must, by their nature, correlate with reality. Pragmatic considerations do not correlate with reality, no matter how pressing they may seem.
Rather than a rational obligation, it is a fact that if a person is irrational then they have no reason to believe that their beliefs correlate with the truth, as they do not. It is merely an assumption they have.
There are all kinds of things that are true in every possible universe that aren’t self-evident. Look up “necessary a posteriori” for examples. So no, self-evident is not the same as necessary, at least not according to a very popular philosophical approach to possible worlds (Kripke’s). More generally, “necessity” is a metaphysical property, and “self-evidence” is an epistemic property. Just because a proposition has to be true does not mean it is going to be obvious to me that it has to be true. Even Descartes makes this distinction. He doesn’t regard all the truths of mathematics to be self-evident (he says he may be mistaken about their derivation), but presumably he does not disagree that they are necessarily true. (Come to think of it, he may disagree that they are necessarily true, given his extreme theological voluntarism, but that’s an orthogonal debate.)
As for your question about standards: I think it is a very plausible principle that “ought” implies “can”. If I (or anyone else) have an obligation to do something, then it must at least be possible for me to do it. So, in so far as I have a rational obligation to have justified beliefs, it must be possible for me to justify my beliefs. If you’re using the word “justification” in a way that renders it impossible for me to justify any belief, then I cannot have any obligation to justify my beliefs in that sense. And if that’s the case, then skepticism regarding that kind of justification has no bite. Sure, my beliefs aren’t justified in that rigorous sense, but if I have no rational obligation to justify them, why should I care?
So either you’re using “justification” in a sense that I should care about, in which case your standards for justification shouldn’t be so high as to render it impossible, or you’re using “justification” in Descartes’s highly rigorous sense, in which case I don’t see why I should be worried, since rationality cannot require that impossible standard of justification. Either way, I don’t see a skeptical problem.
It seems we’re using different definitions of words here. Maybe I should clarify a bit.
The definition of rationality I use (and I needed to think about this a bit) is a set of rules that must, by their nature, correlate with reality. Pragmatic considerations do not correlate with reality, no matter how pressing they may seem.
Rather than a rational obligation, it is a fact that if a person is irrational then they have no reason to believe that their beliefs correlate with the truth, as they do not. It is merely an assumption they have.