But their is a difference between being skeptical, demanding evidence for claims asserted, being empirical, etc. and being an extreme skeptic. In philosophy, extreme skepticism falls into recognizable categories - solipsism and flat-out denialism are the main ones. Denialism, at least, was long ago demonstrated to be internally contradictory, and you can prove it with a simple thought experiment. Simply write on a piece of paper, "This statement is false." This is, of course, absurd - if the statement is true, then it is false, and vice versa. Now, beneath that statement, write "No statements are true." The same contradiction appears.
Solipsism is a trickier position to dismiss. Obviously, I am in no position to disprove the hypothesis that the only thing that exists is my mind. Everything I experience is contingent upon being processed by my mind, and for all I know, I really could be a brain in a vat, being manipulated by stimuli to make my brain see, feel, and react as it does. I have absolutely no way of disproving that. But ask this question: Is such a hypothesis useful? If it were true that nothing I experience is real except my mind, does that describe the world in any meaningful way? It does not. All it leaves is my mind and the great unknown outside my mind, because nothing else can ever be considered real. Even if my brain became aware that it was in a vat being manipulated by electrodes, how does my mind know that that isn't a dream within a dream, as it were? The entire hypothesis becomes effectively meaningless because there's simply no escaping it once you grant the initial premise, and reality just falls apart.
A better way of looking at things is this: We have this world that we experience. We should probably be pragmatic and at least presume that it exists, and go from there. Our experience of the world may be contingent on our minds, and we do well to remember that and consider the effect our mind can have in communicating or miscommunicating the world to us, but it profits us nothing to throw the whole thing away as not existing.
Obviously, when we are in the world we are confronted with limitless claims and assertions. Some of these we accept, some we reject, and sometimes we withhold judgment while awaiting evidence or further discussion. There are myriad philosophical schools as to how we should proceed with respect to which category of assertion. We're not all going to agree on what to do with specific claims, and that's okay.
However, there is a growing movement across the political spectrum to be skeptical for skepticism's sake. 9/11 Truthers deny the narrative of September 11 despite all evidence to the contrary, in favor of some rather outlandish conspiracy theories. Birthers deny the citizenship of Barack Obama even when shown evidence. On and on and on. A key feature of these groups (add bin Laden death denialists to their number) is the rejection of any evidence that contradicts their position, which really makes them not so much skeptics as dogmatists so committed to a given position that no evidence will persuade them.
But that's not really what I'm getting at either. The movement that most annoys me in modern thinking is a ridiculous outgrowth of verificationism that essentially says, "You can believe nothing you haven't witnessed yourself." Obviously, we need to be skeptical about things that other people tell us to believe, but consider how little you actually know if you dismiss anything that you haven't witnessed.
Interestingly, a lot of the force behind this movement comes from religious believers eager to attack scientific positions on the Big Bang, abiogenesis, and evolution. Of course, these believers are perfectly willing to believe that the deity of their choosing created the universe in six days, but that's only because they make a convenient exception to their rules when it comes to their holy books. The argument goes, "Well, you weren't there at the beginning of the universe, so you have no idea what happened, do you?" It gets stronger when you have
I'm on about this because every once in a while you hear people say something like, "I won't believe Osama bin Laden is dead until I see the picture myself." Well, that picture is classified, so the person who says that is going to be disappointed. But the sentiment is understandable. So I guess the question I'm trying to raise in this little discourse is this: What is it in our minds that determines how skeptical we will be with regard to a given claim?
Obviously, each individual is different, but I think a study on the topic would be useful to see why different minds make different choices in where and how to apply skepticism.