What Is Skepticism?
To quote Dr. Shermer: Skepticism is not a position; it's a process.
The popular misconception is that skeptics, or critical thinkers, are people who disbelieve things. And indeed, the common usage of the word skeptical supports this: "He was skeptical of the numbers in the spreadsheet", meaning he doubted their validity. To be skeptical, therefore, is to be negative about things and doubt or disbelieve them.
The true meaning of the word skepticism has nothing to do with doubt, disbelief, or negativity. Skepticism is the process of applying reason and critical thinking to determine validity. It's the process of finding a supported conclusion, not the justification of a preconceived conclusion.
It's thus inaccurate to say "Skeptics don't believe in ghosts." Some do. Many skeptics are deeply religious, and are satisfied with the reasoning process that led them there. Skeptics apply critical thinking to different aspects of their lives in their own individual way. Everyone is a skeptic to some degree.
Skepticism is, or should be, an extraordinarily powerful and positive influence on the world. Skepticism is not simply about "debunking" as is commonly charged. Skepticism is about redirecting attention, influence, and funding away from worthless superstitions and popular misinformation, and toward projects and ideas that are evidenced to be beneficial to humanity and to the world.
The scientific method is central to skepticism. The scientific method is about the study and evaluation of evidence, preferably derived from validated testing. Anecdotal evidence and personal testimonies cannot be tested, so they generally aren't useful to the scientific method, and thus won't often be accepted by a responsible skeptic; which often explains why skeptics get such a bad rap for being negative or disbelieving people. They're simply following the scientific method.
Extraordinary claims require extraordinary evidence, particularly in claims that are far fetched or that violate physical laws. Skepticism is an essential, and meaningful, component of the search for truth.