For a general discussion of skepticism, see Skepticism.Scientific skepticism or rational skepticism (also spelled scepticism), sometimes referred to as skeptical inquiry, is a scientific or practical, epistemological position in which one questions the veracity of claims lacking empirical evidence. In practice, the term is most commonly applied to the examination of claims andtheories which appear to be beyond mainstream science, rather than to the routine discussions and challenges among scientists. Scientific skepticism is different from philosophical skepticism, which questions our ability to claim any knowledge about the nature of the world and how we perceive it. Scientific skepticism utilizes critical thinking and inductive reasoning while attempting to oppose claims made which lack suitable evidential basis. The New Scepticism described by Paul Kurtz is scientific scepticism. 
Like a scientist, a scientific skeptic attempts to evaluate claims based on verifiability and falsifiability rather than accepting claims on faith, anecdotes, or relying on unfalsifiable categories. Skeptics often focus their criticism on claims they consider to be implausible, dubious or clearly contradictory to generally accepted science. This distinguishes the scientific skeptic from the professional scientist, who often concentrates their inquiry on verifying or falsifying hypotheses created by those within their particular field of science. Scientific skeptics do not assert that unusual claims should be automatically rejected out of hand on a priori grounds - rather they argue that claims of paranormal or anomalous phenomena should be critically examined and that such claims would require extraordinary evidence in their favor before they could be accepted as having validity.
Popular targets of criticism among skeptics include psychics, parapsychology, dowsing, astrology, Creationism, homeopathy, tarot reading, alien abductions, and ESP, which sceptics allege are pseudosciences or unsupported by existing evidence. Skeptics such as James Randi have become famous for debunking claims related to some of these. Many skeptics are atheists or agnostics, and have a naturalistic world-view, however some committed skeptics of pseudoscience including Martin Gardner express belief in a God.
From a scientific point of view, theories are judged on many criteria, such as falsifiability, Occam's Razor, and explanatory power, as well as the degree to which their predictions match experimental results. Skepticism is part of the scientific method; for instance an experimental result is not regarded as established until it can be shown to be repeatable independently.
By the principles of skepticism, the ideal case is that every individual could make his own mind up on the basis of the evidence rather than appealing to some authority, skeptical or otherwise.
Skepticism is an approach to strange or unusual claims where doubt is preferred to belief, given a lack of conclusive evidence. Skeptics generally regard it as misguided to believe in UFOs and psychic powers if no empirical evidence exists supporting such phenomena. The Ancient Greek philosopher Plato believed that to release another person from ignorance despite their initial resistance is a great and noble thing. Modern skeptical writers address this question in a variety of ways.
Bertrand Russell argued that individual actions are based upon the beliefs of the person acting and if the beliefs are unsupported by evidence then such beliefs can lead to destructive actions.  James Randi also often writes on the issue of fraud by psychics and faith healers.  Critics of alternative medicine often point to bad advice given by unqualified practitioners, leading to serious injury or death. Richard Dawkins points to religion as a source of violence, and considers creationism a threat to biology. Some skeptics support opposition to some cults and new religious movements because of their concern about what they consider false miracles performed or endorsed by the leadership of the group. They often criticize belief systems which they believe to be idiosyncratic, bizarre or irrational. See also Allegations against cults made by skeptics.
. James Randi. Flim-Flam! Psychics, ESP, Unicorns, and Other Delusions. Prometheus Books. June 1982. 342. 0345409469.
. James Randi. Arthur C. Clarke. An Encyclopedia of Claims, Frauds, and Hoaxes of the Occult and Supernatural. St. Martin's Griffin. 1997. 336. 0312151195.
. Carl Sagan. Ann Druyan. The Demon-Haunted World: Science as a Candle in the Dark. Ballantine Books. 1997. 349. 0345409469.
. Martin Gardner. Fads and Fallacies in the Name of Science. Dover Publications. 1957. 373. 0486203948.
. Paul Kurtz. The New Skepticism: Inquiry and Reliable Knowledge. Prometheus Books. 1992. 371. 0879757663.
. Michael Langone. Recovery from Cults: Help for Victims of Psychological and Spiritual Abuse. W. Norton. American Family Foundation.. June 1995. 432. 0393313212.