Freethought is a philosophical doctrine that holds that beliefs should be formed on the basis of science and logical principles and not be comprised by authority, tradition or any other dogmatic or other belief system that restricts logical reasoning. The cognitive application of freethought is known as freethinking, and practitioners of freethought are known as freethinkers.

Freethought holds that individuals should neither accept nor reject ideas proposed as truth without recourse to knowledge and reason. When applied to religion, the philosophy of freethought holds that, given presently-known facts, established scientific theories, and logical principles, there is insufficient evidence to support the existence of supernatural phenomena.