Skepticism has many definitions, but generally refers to any questioning attitude towards knowledge, facts, or opinions/beliefs stated as facts, or doubt regarding claims that are taken for granted elsewhere. The word may characterise a position on a single matter, as in the case of religious skepticism, which is "doubt concerning basic religious principles (such as immortality, providence, and revelation)", but philosophical skepticism
Philosophical skepticism
Philosophical skepticism is both a philosophical school of thought and a method that crosses disciplines and cultures. Many skeptics critically examine the meaning systems of their times, and this examination often results in a position of ambiguity or doubt...

 is an overall approach that requires all new information to be well supported by evidence.

Scepticism is the first step towards truth.

Denis Diderot, Pensées Philosophiques (1746)

History is replete with examples of what happens when any group of authorities do not have to answer to empirical evidence but are free to define truth as they see fit. None of the examples has a happy ending. Why should it be otherwise with therapy?

Robert Todd Carroll, The Skeptic's Dictionary, entry on "repressed memory therapy (RMT)"

A danger sign of the lapse from true skepticism into dogmatism is an inability to respect those who disagree.

Dr. Leonard George|Leonard George

You can get into a habit of thought in which you enjoy making fun of all those other people who don't see things as clearly as you do. We have to guard carefully against it.

Carl Sagan, in "The Burden of Skepticism" (1987) on Marcello_TruzziPseudoskepticism|pseudoskepticism.

The chief deficiency I see in the skeptical movement is its polarization: Us vs. Them — the sense that we have a monopoly on the truth; that those other people who believe in all these stupid doctrines are morons; that if you're sensible, you'll listen to us; and if not, to hell with you. This is nonconstructive. It does not get our message across. It condemns us to permanent minority status.

Carl Sagan, in The Demon-Haunted World : Science as a Candle in the Dark (1996), p. 300