If they're trying to use the argument in a practical situation (such as trying to use skepticism to "prove"/"disprove" God/gods), then sure; but both times you've said this is in threads about absolute knowledge, where theory and not practice is the subject. Or atleast, that's the impression I've gotten, as CecilSunkure seems to be often trying to disprove it on logical grounds... and then ending up with arguments against it grounded in practice ("reasonab[ility]").

It was made in reference to knowledge which is uncertain; the statement itself is, in part, pointing out that the knowledge is uncertain.
It's useless and unprovable, but it's not meaningless, as it posits a possibility which is entirely, er, possible, as it remains to be disproven, and by its own claim is undisprovable, which is also yet to be disproven [ad nauseum] ...

If the knowledge is uncertain knowledge, then it is still knowledge nonetheless, especially if the claimer knew of the uncertainty. But I think you meant that the claim may or may not be true. Although, if the person making the uncertain claim knows its uncertainty, he contradicted his original premise.

It's meaningless if it came from someone who supposedly doesn't know what they are even saying.

Sure, you can treat the claim as standalone, and ignore the fact that the person claiming isn't supposed to know its meaning, but what I was making the point is that:

I think it's important to make a distinction between what is and is not knowledge. It's a hard thing to define, but in general we can call it absolute certainty of a fact + that the abolute certainty is correct about the fact. Under this manner of thinking, "uncertain knowledge" is not possible, it's not knowledge, it's something else.

Something relevant, from an old ghost who went to study math and stopped having time for SEN, lately.

What I'm going to cite is the so called incompleteness axiom from mathematics. Say you want to be able to have a statement that says "This statement cannot be proven." If we prove the statement, the statement is false, which is a contradiction. However, if we disprove the statement, we prove that it is possible to prove it, which is a contradiction. If the statement is false, it can be proven to be true, which is also a contradiction. If the statement is true, then it cannot be proven, which is not a contradiction. However, we have, in the previous arguments, shown that it is true. As such, our arguments cannot constitute a full proof of the argument, but we have used the to know, with full certainty, that it is impossible to prove the statement, which is the assertion of the statement itself. This

I don't claim to fully understand incompleteness, it's a rather messed up topic, and the proof is exceptionally hard to follow. Anyways, what I might suggest to the OP's question, is that some things have to be known without verification. How do you know that you need to verify something in order for it to be true? Or can you not look at an apple and say "I perceive this object that has been defined to be an apple", without a shadow of a doubt? Now, if someone asked you why, your only response could be "because it is so", which is effectively declaring the fact that you perceive to be axiomatic in nature, which by definition is either self-verifying or does not require verification. Self verification is basically outlined as follows "If X, X. If not X, X. Thus X." Basically, find a statement that shows itself to be true if you assume it is false, but that works if you assume it to be true. The Completeness argument sort of works that way, because it's either true, or you can prove it to be true.

http://en.wikipedia.org/wiki/G%C3%B6del%27s_incompleteness_theorems

Well I find there are basically two ways of knowing something:

1. Do-it-yourself. Eg. burning your hand on the stove, you KNOW through your perceptions that the stove is fucking hot, and not to touch it again!

2. Told-by-another. Eg. your teacher telling you facts about some subject or another.

Simply put, 1. is a lot more reliable then 2. That being said, 1. is also not without its flaws, your brain may misinterpret your perceptions, or your sensory organs may be sending you false readings (like when you smoke pot). But for the most part you can trust your perceptions and the information they tell you. Whereas a lot of information from 2. should also be verified either by method 1. or by numerous methods of 2.

The dilemma at hand: 1. is much more time consuming then 2., we don't have enough time to prove everything ourselves, that is why we resort to 2. So the next dilemma becomes how to validate 2. and mostly this is done by numerous validations by 2. indirect validations by numerous 1. or the good old do it yourself 1.

Long story short, we can not TRULY know anything, but we can be REASONABLY SURE, and the closest to TRUE KNOWLEDGE is direct validation by 1. Everything from 2. you should not believe blindly.

I'll just give you a couple funny examples before I go:
Back in the medieval times: everyone KNEW the Earth was flat, every KNEW the Earth was the center of the universe. They all KNEW this through 2., because it was next to impossible to prove with 1. until much later.

Its just funny to think, I wonder in 200 years time, what will we KNOW then?

If anyone has any disagreements with my theory please comment I welcome it and always willing to look over things, after all we are humans we make errors, and we don't KNOW anything for sure!

Well... apart from being over-simplified and using caps lock for "know" each time, your idea doesn't really say much. First thing is that if you touch the stove and you get burned, you had to make the connection that burns come from hot things, and you somehow inferred that the stove would burn you if you touched it again. But you didn't touch it again, did you? Essentially, it's the "scientist and the button" problem, which is basically that if there was a button that shocked you when you touched it, a scientist could never know for sure if the button shocked you each and every time you touched it, but the amount of certainty with which he could say it did depended entirely on how many times he would press the button and receive a shock.

That being said, your example doesn't work without redefining knowledge, so that "knew" is the same as "believed." Knowledge is generally referred to as "justified, true, belief," which means that in addition to believing something, you need a reason to believe it, furthermore this reason needs to be so solid and indisputable that it also provides an absolute proof that the belief is true.

Anyways, sense perception isn't going to cut it, if you're looking to define knowledge, truth, etc. I recommend watching the Matrix again, if that doesn't make sense, because 1. It's almost identical to the principle of Descartes' thought experiment and 2. It's an awesome movie.

I can know anything I define, but my definitions are not real. I cannot know anything real. I can know everything I understand though, because all that I understand is not real. I cannot understand anything I don't make up. I cannot make up what I do not have a seed of information for. I cannot get seeds of information except from reality. But I cannot know reality, so I cannot be sure what the information pertains to. Thus my inference to knowledge from such information may will always be flawed. However, as the information collected increases, my inference from such information becomes better and better. Eventually, we will be able to make statements about the function of things to a reasonable degree of accuracy. But then again, the universe functions in a probable way, always going towards energetically degenerate states because there is more probability of their existence. So I can probably know everything at some point, but until then I cannot really know anything.