I'd already considered the "What the Tortoise said to Achilles" argument in a different form. I'd gotten around it (I was arguing Foundationalism until now, remember) by redefining self-evident as:
What must be true in any possible universe.
If a truth is self-evident, then a universe where it was false simply COULD NOT EXIST for one reason or another. Elizier has described a non-Reductionist universe the way I believe a legitimate self-evident truth (by this definition) should be described. To those who object, I call it self-evident' (self evident dash, as I say it in normal conversation) and use it instead of self-evident as a basis for justification.
The Foundationalist skeptics in the debate would laugh at your argument, point out you can't even assume the existence of a brain with justification, nor the existence of "should" either in the human sense or any other. Thus your argument falls apart.
I agree with the foundationalist skeptics, except for that anything "falls apart" is, of course, something that they just assume without justification, and should be discarded :)
I have naturally read the material here, but am still not sure how to act on two questions.
1: I've been arguing out the question of Foundationalism v.s Coherentism v.s other similiarly basic methods of justifying knowledge (e.g. infinitism, pragmatism). The discussion left off with two problems for Foundationalism.
a: The Evil Demon argument, particularly the problem of memory. When following any piece of reason, an Evil Demon could theoretically fool my reason into thinking that it had reasoned correctly when it hadn't, or fool my memory into thinking I'd reasoned properly before with reasoning I'd never done. Since a Foundationalist either is a weak Foundationalist (and runs into severe problems) or must discard all but self-evident and incorrigible assumptions (of which memory is not one), I'm stuffed.
(Then again, it has been argued, if a Coherentist were decieved by an evil demon they could be decieved into thinking data coheres when it doesn't. Since their belief rests upon the assumption that their beliefs cohere, should they not discard if they can't know if it coheres or not? The seems to cohere formulation has it's own problem)
b: Even if that's discarded, there is still the problem of how Strong Foundationalist beliefs are justified within a Strong Foundationalist system. Strong Foundationalism is neither self-evident nor incorrigible, after all.
I know myself well enough to know I have an unusually strong (even for a non-rationalist) irrational emotive bias in favour of Foundationalism, and even I begin to suspect I've lost the argument (though some people arguing on my side would disagree). Just to confirm, though- have I lost? What should I do now, either way?
2: What to say on the question of skepticism (on which so far I've technically said nothing)? If I remember correctly Elizier has spoken of philosophy as how to act in the world, but I'm arguing with somebody who maintains as an axiom that the purpose of Philosophy is to find truth, whether useful or useless, in whatever area is under discussion.
3: Finally, how do I speak intelligently on the Contextualist v.s Invariantist problem? I can see in basic that it is an empirical problem and therefore not part of abstract philosophy, but that isn't the same thing as having an answer. It would be good to know where to look up enough neuroscience to at least make an intelligent contribution to the discussion.