Deism (/ˈdɪzəm/ DEE-iz-əm[1][2] or /ˈd.ɪzəm/ DAY-iz-əm; derived from Latin deus, meaning "god")[3] is the philosophical position and rationalistic theology[4] that 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.[3][4][5][6][7][8] Deism is also defined as the belief in the existence of God solely based on rational thought, without any reliance on revealed religions or religious authority.[3][4][5][6][7] Deism emphasizes the concept of natural theology, that is, God's existence is revealed through nature.[3][4][5][6][8]

Since the 17th century and during the Age of Enlightenment, especially in 18th-century England and France, various Western philosophers and theologians formulated a critical rejection of the religious texts belonging to the many institutionalized religions and began to appeal only to truths that they felt could be established by reason alone as the exclusive source of divine knowledge.[4][5][6][7] Such philosophers and theologians were called "Deists", and the philosophical/theological position that they advocated is called "Deism".[4][5][6][7] Deism as a distinct philosophical and intellectual movement declined towards the end of the 18th century.[4] Some of its tenets continued to live on as part of other intellectual movements, like Unitarianism, and it continues to have advocates today.[3]