Freethought holds that individuals should neither accept nor reject ideas proposed as truth without recourse to knowledge  and reason. Thus, freethinkers strive to build their opinions on the basis of facts, scientific inquiry, and logical principles, independent of any logical fallacies  or the intellectually-limiting effects of authority, cognitive bias, conventional wisdom, popular culture, prejudice, sectarianism, tradition, urban legend, and all other dogmatic or otherwise fallacious principles. Applied to religion, freethinkers have generally held that there is insufficient evidence to support the existence of supernatural  phenomena.

A line from "Clifford's Credo" by the 19th Century British mathematician and philosopher William Kingdon Clifford perhaps best describes the premise of freethought: "It is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence."

-WIkipedia