In the hopes of enlightening the reader in the fine art of skepticism, I have decided to construct a brief primer on the subject.
The word skeptic comes from the Greek σκεπτεον, which, according to Liddell and Scott’s Greek-English Lexicon, means “one must consider or look closely at.” According to the same source, it is derived from σκεπτομαι, which means, among other things, to look closely at. In most philosophy and science classes, students are told that it means something like “to inquire” or “to investigate,” which are also accurate definitions. Originally, skepticism was a school of thought that argued that the route to knowledge was rational inquiry. That holds for most skeptics today.
Today, skepticism had come to be synonymous with doubt. This is also accurate, but it holds unnecessary negative connotations. I prefer to think as skepticism as the school of thought that claims should be backed up with evidence that is backed by either sound logic or sound science or both. The more outlandish the claim, the more evidence is needed. In fact, the oft-quoted motto of skeptics everywhere is extraordinary claims require extraordinary proof. Curing cancer with lifestyle changes, existence of a life force, seeing the future, communing with the dead, and definite knowledge of God are all extraordinary claims, and therefore require extraordinary proof. In essence, an extraordinary claim is anything that would require rewriting our entire knowledge of science, logic, or philosophy.
One can be skeptical of anything, and in fact, most people are skeptics in some way. For instance, some paranoid conspiracy theorists are skeptical of the fact that the Apollo 11 mission in 1969 landed two Americans on the moon. Most creationists are skeptical of rationalist theories of evolution. One needs to be skeptical some of the time, otherwise one ends up believing everything. Likewise, one should not be skeptical of everything, otherwise one ends up believing nothing.
I tend to be a classicist in my skepticism in that I believe that the only certainty is that we cannot be certain of anything. This is one of the oldes schools of skepticism, dating back to ancient Greece. (Another Greek school of skeptics held that we can never truly know anything, which I think is rather absurd.) I choose to go by likelihood. I believe that we can use our understanding of logic and the natural world to deduce which of a set of competing claims is most likely or probable, and that we should always give that claim the most credence until enough contrary or contradictory evidence refutes that position. I also make ample use of Occam’s razor to rule out those proposed theories which posit unnecessary pluralities.
In general, the best way to be skeptical is to consider all of the data, but weight that data which was most rigorously gathered and has a foundation in established science or philosophy more than that which is sloppily gathered or goes against established common knowledge. Also, withhold judgement on new claims until you have examined enough data to determine whether or not that claim is plausible or probable. It helps to take a class in logic (any philosophy department at any college or university will have one, so audit it if you can). If you can find a class on the scientific method, that would help too. And always think analytically; intuition is fine for small, day-to-day decisions, by all knowledge of the natural world should come from serious analysis and critical think. I tend to be a strict rationalist, and as such I think this is the only true route to knowledge.
I hope this has helped for those of you who might be new to skepticism or who might not fully understand it.