Let me say that I think that's a very clever argument. :)  Now I'll try (unsuccessfully I imagine) to challenge it a bit...

There are Christians who maintain that the existence of god is provable without recourse to faith; strictly via evidence and logic.  As they hold that god is omnipotent, they surely don't believe that he doesn't wish to be proven (or, if he does, that at least he doesn't stop them from doing it).  While not every Christian will agree on this point, it does slightly challenge the notion that a god with the attributes you've mentioned is at the heart of every major religion.  Maybe, within various religions, some view god in the way you suggest, while others believe that god is provable.

So, at the least, we could imagine an anti-theist with an airtight argument against all possible provable gods (and I agree that would be a tall order), leaving only those with the power and inclination to remove themselves from proof altogether.

Of course, this won't satisfy us.  For our anti-theist to escape being faith-based, he must be able to prove against all possible gods, and especially those who refuse to be proved, which seems insoluable.

I can only observe that our interest here isn't in saying anything, one way or another, about god--our interest is in whether there can never be an anti-theist who could prove that god cannot exist.  What if there was an anti-theist who was as powerful as the god we're supposing?

I mean, as long as we're supposing an omnipotent god, why can't we suppose an uber anti-theist with the power to construct airtight proofs for all that is (and against all that isn't)?

Now... I imagine that a person could say either that the powers of the omnipotent god and the uber anti-theist somehow would cancel each other out, or that the supposition of an omnipotent god renders the uber anti-theist impossible, as the uber anti-theist's existence would be a limit on the god's power to remain aloof from proof.  But, by that same rationale, supposing the uber anti-theist would render the omnipotent god impossible, as its existence would be a limit on the anti-theist's ability to construct proofs.  And I see no compelling reason to give priority to an omnipotent god over an uber anti-theist.

Yeesh.

Actually there is compelling reason to give the preference to God.  Because if it/he wasn't the more powerful one you've then begged the question (sort of).  Your scenario assumes that god is not omnipotent to prove that he doesn't exist. If the contention is a god that is omnipotent and you disprove him by assuming he is not omnipotent the proof is invalid.

I've resorted to absolute nonsense to maintain my point here, and it makes me feel all slimy.  But I think it conceivable, at least, that an uber anti-theist is not more nonsensical than an omnipotent god.  And I wonder, is it possible to prove that an uber anti-theist cannot exist (without resorting to the same kinds of faith-based pronouncements that the less powerful anti-theists are supposed to make)?

Nonsense?  I don't know that I would say that, I think this sort of suppositional roll in the dirt, so to speak, is what is appealing about the topic.  Assert some thing about god and or his power and then consider what lines of thought and reasoning it opens.  As an example I have a devoutly atheist friend (in the sense I refer to it) and he points out that God's love for mankind is actually a weakness which contradicts his omnipotence. When I pointed out that this doesn't actually disprove God, he thought for about 5 minutes before looking up at me and said "but it IS a weakness!...and if I can find a way to exploit it I can take his place".  He was purely joking of course, but my point is it opens up new thoughts on how to approach an issue. Even if they prove fruitless, it is one more thing you've considered, one more thought you might be able to draw on later, etc..

I wholeheartedly concur.

I only want to observe that "probably everyone" is not "provably everyone," which I know you know, but I think it's an important point.  And not just for the anti-theist's sake; if we allow that some God might exist, and that it might be a God open to being proved... then maybe, somewhere, there is a theist who has that proof?

Also, should any given theist or anti-theist advance what he claims to be a logical argument regarding god's existence, I don't think that we can dismiss his argument prima facie (because it purports to do something we believe is inherently impossible), but it would be an argument like any other, and should stand or fall based on its merits.

I'm not opposed to keeping an open mind...even when logic does support your argument.  The prime example of why this is a good idea was actually the subject of a rather intense scientific debate over whether light was a particle or a wave.  Gassendi and later Isaac newton supported the particle theory while Hooke, Huygens, and later Young supported the idea of it being a wave.  Well to make a long story short they were both right, and after Young showed expirimentally that it did behave like a wave it took a long while before the issue was properly addressed and it was discovered it actually has what is now known as a wave-particle duality.

Science has actually proven very bad at remembering such issues...comes with the personality attracted to the career perhaps.

So long as "non-theist" continues to mean "anti-theist" in the sense that I've been using (and that I believe you mean), we're in total agreement on these points.

***

I think that maybe we're still short of establishing what I feel like you were saying earlier (even ignoring "atheist" vs. "anti-theist"), when I thought you were claiming that anti-theism was necessarily faith-based.  But perhaps that's either no longer your position, or you are unconvinced by my supposition of an uber anti-theist.

I mean, I'm unconvinced by it, too, so I can't expect different from anyone else. :)  But logically, I can't see how it's different in nature to suppose the uber anti-theist versus the omnipotent god who doesn't want to be proven.  And, as long as we can't prove that the uber anti-theist cannot exist, I don't think we can be... uh... anti-anti-theist.

Yeesh, again.

It's different because you're only proposing one possibility. The "uber-theist" AND "God" possibility doesn't nullify the other possibility of just "God" alone.  Or to put it another way it's sort of like saying "Fred may have an umbrella with kittens on it"...that statement is still possibly true even if you then add "Fred may have an umbrella with kittens on it and a cat skinning knife".  And of course only one possibility needs to be true for there to be a counterpoint.

No, no--I'll take accuracy over simplicity every time. :)

Okay.  If we grant all of that, then how do you propose we come to the specific interpretations that we do?  Also, why does there seem to be such wide agreement in basic interpretations?  (Examples like the "piano" pic you'd posted are crafted to ellicit specific interpretations; that craft suggests that the form is purposeful, don't you think?)

I'll understand if your feeling is that, you don't have to determine these things for your general skepticism to stand, but I'm still interested as to what you think about them, given your more fundamental position.

"Confusion"
I believe this is commentary/introduction that does not require a reply. 

"My Fundamental Issue"
"I only now began using the term “legitimate’ in place of “arriving at absolute knowledge through a method of truth”."
     I interpret this to mean that a "legitimate belief" by your definition is "a belief whereby one can apply a method of truth to arrive at absolute knowledge."  I do not see what else could be meant here. 

Now, unless "method of truth" means something TRULY bizarre, this implies to me that you have the position that no legitimate beliefs exist that interpret sense data.  Since that would mean getting absolute knowledge out of sense data. 

So when you said "any belief set is supported by sense data" (and you now say that you meant "legitimate belief" instead of "ANY belief"), it makes no sense to me that you meant "any set of beliefs whereby one can apply a method of truth to arrive at absolute knowledge is supported by sense data", this makes no sense because you also have the position that sense data cannot be reliable evidence at all.  Therefore sense data can neither support nor discredit a legitimate belief, since it by necessity does not rely on sense data.  ...wait.
     Okay, forgot that you just meant "is consistent with" instead of actually "supports".  But ... wait again. 

IMO either your explanation or your previous posts are complete nonsense.  Behold: 
     "I thought it was understood but what I was referring to was AT ANY POINT in your sense data it could support any* worldview/belief. If a guy changes his mind over a period of time from a different interpretation of sense data… well then, ya, he’s contradicted his original interpretation. He’s changed his belief on the matter.
     "*What I mean by ‘any’ and ‘anything’ in context here is anything that you can find to fit with sense data, which I figure is infinite. Now, I’m not necessarily saying every belief would fit with sense data (e.g. regarding knowledge of sense data itself: we sense what we call the color blue and believe it’s actually red)."
     Here you appear to be claiming that your statement is accurate because even though his worldview (now "belief set" or supposedly "legitimate belief set") has contradicted what it used to be, its changed state is still supported by the sense data so it's all good.  You appear IMO to mean "interpretation of sense data" when you say "belief".*  I do not understand how your previous explanation is compatible with your current explanation.  Notably, how is it possible for a legitimate belief to be contradicted, if it is a method of absolute truth? 

*Further evidence:  "He lands on the moon and could now believe either 1. The ‘cheese moon’ apparently turned to rock by a scientific phenomenon well beyond his explanation. 2. God, again, changed the moon to rock while in flight 3. He’s hallucinating. 4. The cheese got very hard and changed color. Etc. (Need I say again, the Matrix murders all hope in interpreting correctly or looking for consistency or probability.)"
     "I've said our judgements on sense data are totally arbitrary (apart from consistency), so any judgement you make could be made to fit any theory. Like the Matrix: "Everything is a simulated computer experience, and everything I sense is made to perfectly fit what would be sensed otherwise.  I sense this and detect nothing unusual" would make perfect use of sense data judgement." (This is the  ancestral post that started this.)

I DEMAND YOU TELL ME EXACTLY WHERE I WENT OFF THE RAILS (ALL THE PLACES) FROM YOUR REASONING OR DEFINITIONS OR POSITIONS OR ANYTHING IN THE ABOVE SECTION! 

The Rest ("Side Note", "B.", and "Conclusion")

So, THIS ENTIRE TIME, for pages and pages, you have been thinking that I was trying to derive a way to arrive at absolute knowledge.  This despite pages and pages of me saying that I am doing no such thing.  Urge to kill...rising. 

If you thought I was trying to do something I said IN THE SAME BREATH that I wasn't trying to do, you should have fucking spoken up.  I realize that you said, "I don't understand", but you should have said "I don't understand:  it looks to me like you are contradicting yourself and here's why." 

I'm not entirely sure what you mean by "would that embody your issue with empiricism – to arrive at ‘practicality’?"  My goal is to show that empiricism is practical, not that it is a WAY to "arrive" at practicality, whatever that means, although I have my suspicions. 

As for BWIB, KWIB, input/output etc. being introduced separately, I did put them all together in a post recently for your convenience. 
http://www.vgchartz.com/forum/post.php?id=2005591
(I also put together a montage of me saying this part of the discussion isn't about absolute knowledge.)
http://www.vgchartz.com/forum/post.php?id=2009969

So I am certainly not trying to establish absolute knowledge via empiricism, and I am frankly astonished that you have managed to hold on to that misconception with such incredible tenacity. 
     As for practicality, I am trying to show that empiricism is the practical belief set type (vs. non-empiricism-based ones).  See the second link just above for a partial definition of practicality I gave.  Also, usefulness or utility might be synonyms for this purpose.

   I don’t think it’s possible for me to respond to so much of what was said. We must truly be speaking a different language now. The use of our terms here is beyond me. Like when you said “this implies to me that you have the position that no legitimate beliefs exist that interpret sense data” I literally had an argument with my brother on what this meant for about half an hour.

   I kept up the issue of absolute knowledge because I felt that what you were saying continuously addressed something in relation to truth, whether you believe that or not (and that will be our new issue to decide that). And whatever you were saying seemed to continuously deny the point I was making on the empirical method, which had me thinking you understood that I was indeed making a point in regards to absolute truth (method of truth).

   I would love to start anew and explain my position, regarding absolute knowledge in relation to empiricism, from the ground up, taking extra precaution to over-explain with the former misunderstandings in mind, but it may not matter since one thing seems clear: that you believe “empiricism is practical” is different from gaining absolute knowledge.

   So… I’ll just respond to that (as I do believe it will actually relate to my absolute knowledge bit in the end). My attempt here now is to blur the distinction between “practical whatever” (via empiricism) and ‘absolute knowledge’.

   I’ll take the Socratic approach as I’m still a little curious as to what you mean. What do you mean when you say empiricism is practical? What do you mean by saying sense data is all we have? (If we were talking about a method of truth for absolute knowledge I’d say that empiricism was not the only proposed method of truth).

   Does this mean you believe something about what is being presented to you through sense data? If not, what are you saying is occurring with sense data on this ‘practical level’.

   I promise I’m trying to present this as neutral as possible. Any apparent sarcasm is just a result of me being at a loss of explaining your position myself.

Actually there is compelling reason to give the preference to God.  Because if it/he wasn't the more powerful one you've then begged the question (sort of).  Your scenario assumes that god is not omnipotent to prove that he doesn't exist. If the contention is a god that is omnipotent and you disprove him by assuming he is not omnipotent the proof is invalid.

   As annoying as it may be, it must be pointed out that the belief that there is a wide agreement on basic interpretations is only an interpretation as well. It must be admitted that epistemology is taking place in... our head. Common sense, obviousness, and the like is in our head and epistemology isolates it, making all belief on the external world and it's nature equal.

   As for a method of truth... I'm afraid I must claim a seemingly fatuous method to the mind of most, but, to be fair, (if you believe some history on epistemology) a method that has also been acknowledged by equally 'great minds' in regards to epistemology as well. Merely that of revelation. It holds no process or application, only the reception of knowledge from that which imputes knowledge. And what I mean by that is, one is at the mercy of that which holds knowledge (although it may be called the act of presupposition from a certain perspective). Hate to sound all mystical. It just works as an answer to epistemology and the only one that doesn't hold a problem as far as I have understood.

   In short, how do we know? By receiving it from that which has knowledge. Any other belief, from anywhere, I don't give the same confidence (I 'step lightly').

   Although uniqueness isn't an indication of truth, I think this method of truth is unique to biblical christianity. Opponents share an attempt to reach truth "by the power of man" in rationalism, empiricism, or subjectivist doctrines (e.g. Atheism, Islam, Hinduism). All of which I find either contradictory or based on false statements exposed by recognizing possibilities in the mind.

I don't think that I am begging the question.  Instead, I think that we are changing the question: we started off by saying that, for an anti-theist to avoid having "faith-based" beliefs, he would have to be able to prove them (according to the means already discussed).  And I suggested that, while this is true, we haven't established that proving anti-theism is impossible, which we would have to do in order to make the general case that anti-theism is faith-based.

So, to prove that proving anti-theism is impossible, you posited an god who doesn't want to be proven.  To counter, I posited an uber anti-theist with the power of perfect proving/disproving ability (or, actually, it doesn't have to be an "uber anti-theist"; it could be any non-god entity with that power); such a being would theoretically be able to construct an airtight argument against any possible god, assuming that god doesn't actually exist (because, if god did exist, then my uber anti-theist would quickly become an uber theist).

Assuming that god doesn't actually exist for my uber anti-theist is a hefty qualifier, and yet absent being able to metaphysically determine whether or not a god actually exists--apparently beyond both of us, for obvious reasons :)--we cannot say for certain that such an uber anti-theist could not exist.  It is not begging the question to dismiss god in this scenario, because the proposition at issue was not, "could an omnipotent god exist," but "could there exist an airtight argument that god does not exist"?  And it is theoretically possible, if we happen to to live in a universe in which there is no god, which is not something that either you or I claim to know for sure.

To say "an omnipotent god is possible, therefore such an argument is impossible" isn't quite correct... rather, an omnipotent god is possible, therefore a logical argument proving no god exists is possibly impossible; it doesn't discount that such an argument is also possibly possible--in a universe where an omnipotent god doesn't, in fact, exist, opening the door for the possibility of an uber anti-theist.

Yeesh, the third.

Thats where the "(sort of)" came in actually.  In order for your uber theist to be part of the same possibility it would beg the question, but it could also legitimately be part of another possibility which would not be begging the question.  But as a distinct possibility on its own it doesn't help the argument along because it is distinct and does nothing to disprove the other possibility.

To look at it another way, if I'm guilty of begging the question here, we both are: we cannot rule out an airtight argument against god.  The only universe in which such an argument could not exist would be one that has the omnipotent god you'd suggested; we can only disprove the possibility of such an argument by proving that god does, in fact, exist.  And so... if we can't do that, then we can't disprove the possibility of such an argument.

I can't actually beg the question in this instance though, since I'm not asserting the truth of the possibilities I'm putting forward I'm never actually relying on the assumptions I'm making as part of any proof.  This is what is really clever about the argument actually, because to disprove god you must show that all cases have been handled I only have to offer up a single case where it is logically impossible to disprove god and I make my point...I'm not actually trying to prove that the possibility is correct (I know I can't because if I did it this way I would be begging the question).  I only need it to remain possible.

So, I would say that neither an omnipotent god nor an uber anti-theist can be proven against... or, at least, not by me, and I suspect not by you, either.  And if we can't prove against either, then maybe the real conclusion is:

Neither theism nor anti-theism are necessarily faith-based.

In order for your uber theist to be part of the same possibility it would beg the question, but it could also legitimately be part of another possibility which would not be begging the question.  But as a distinct possibility on its own it doesn't help the argument along because it is distinct and does nothing to disprove the other possibility. 

Well, then, a universe in which an omnipotent god exists (but not an uber anti-theist) is a distinct possibility.  And a universe in which an uber anti-theist exists (but not an omnipotent god) is a distinct possibility.  And supposing either takes nothing away from the other supposition.

And we're caught here:  we don't know which of these universes we live in.

And so, barring any means by which we could determine which of those universes we live in, we have to admit that both remain possible.  And, so long as it is possible that we live in a universe with an uber anti-theist, then it is also possible that there exists an airtight argument against the possibility of a god.

And as long as that possibility exists, we can not logically say that anti-theism is necessarily faith-based.

Do you disagree?