Freethought is an epistemological viewpoint which holds that beliefs should not be formed on the basis of authority, tradition, revelation, or dogma, and should instead be reached by other methods such as logic, reason, and empirical observation.

Deism is the philosophical position and rationalistic theology that generally rejects revelation as a source of divine knowledge and asserts that empirical reason and observation of the natural world are exclusively logical, reliable, and sufficient to determine the existence of a Supreme Being as the creator of the universe. More simply stated, Deism is the belief in the existence of God, solely based on rational thought without any reliance on revealed religions or religious authority. Deism emphasizes the concept of natural theology—that is, God's existence is revealed through nature.