Now that I have presented the difference between skepticism and denialism, I want to clear up what exactly skepticism is. Since he is perhaps one of the greatest champion of skeptical thought and is great at demonstrating ideas in a way that is easily understood, I will be borrowing much from Carl Sagan (specifically his chapter in The Demon-Haunted World of the same title as this post).
Sagan described skepticism as a Baloney Detection Kit, which contains the tools "to construct, and to understand, a reasoned argument and -- especially important -- to recognize a fallacious or fraudulent argument."
So, what's in the tool kit? There is a list of do’s and a list of don’ts.
• Independently confirm the "facts" wherever possible.
• Encourage substantive debate on the evidence by knowledgeable proponents of all points of view.
• Spin more than one hypothesis. If there's something to be explained, think of all the different ways in which it could be explained. Then think of tests by which you might systematically disprove each of the alternatives. What survives, the hypothesis that resists disproof has a much better chance of being the right answer than if you had simply run with the first idea that caught your fancy.
• Quantify. If whatever it is you're explaining has some measure, some numerical quantity attached to it, you'll be much better able to discriminate among competing hypotheses.
• Make sure arguments follow. If there's a chain of argument, every link in the chain must work (including the premise) -- not just most of them.
• Use Occam's Razor. This convenient rule-of-thumb urges us when faced with two hypotheses that explain the data equally well to choose the simpler.
• Ask whether the hypothesis can be, at least in principle, falsified. Propositions that are untestable, unfalsifiable are not worth much.
• Perform controlled experiments wherever possible.
• Use arguments from authority, as they carry little weight -- "authorities" have made mistakes in the past. They will do so again in the future. Perhaps a better way to say it is that in science there are no authorities; at most, there are experts.
• Get overly attached to a hypothesis just because it's yours. It's only a way station in the pursuit of knowledge. Ask yourself why you like the idea. Compare it fairly with the alternatives. See if you can find reasons for rejecting it. If you don't, others will.
• Use logical fallacies.
So that's the basic gist of skeptical thinking right there. As someone who is rather innately gullible, I find these tools to be extremely useful.
In fact, everyone tends to find use of skeptical thinking in some aspects of their life. For instance, I am currently looking to buy a car. Most people apply skepticism to such an endeavor. For instance, when I go look at a car tomorrow, I'm going to bring my father (who worked as a mechanic for some time) with me because I really don't know a lot about cars, and I know he can ask the right questions and spot anything obviously wrong. This is what skeptics do, but they apply it to more things than just car purchases. They hopefully apply it to religion, economics, politics, and general claims about how our world works.
I can say with reasonable certainty that skepticism works. Science wouldn't be what it is without skepticism (they are really the same thing), and the world simply wouldn't be the same without science. It is that skepticism that breeds valid claims, and rejects invalid ones. Skepticism allows for a meaningful progression of knowledge; knowledge that we can apply to improve not only our understanding of the world around us, but our mastery of it. But, please, don’t take my word for it — try it for yourself.