Dawkins is an outspoken atheist and a supporter of various atheist, secular, and humanistic organisations. He is a patron of the British Humanist Association, and a supporter of the Brights movement. He was confirmed into the Church of England at the age of thirteen, but began to grow sceptical of the beliefs. After learning about Darwinism and the real scientific reason why living things look as though they have been designed, Dawkins lost the remainder of his religious faith. He said that his understanding of science and evolutionary processes led him to question how adults in positions of leadership in a civilized world could still be so uneducated in biology, and is puzzled by how belief in God could remain among individuals who are sophisticated in science. Dawkins notes that some physicists use 'God' as a metaphor for the general awe-inspiring mysteries of the universe, which causes confusion and misunderstanding among people who incorrectly think they are talking about a mystical being which forgives sins, transubstantiates wine, or makes people live after they die. He disagrees with Stephen Jay Gould's principle of nonoverlapping magisteria (NOMA) and suggests that the existence of God should be treated as a scientific hypothesis like any other.
On his spectrum of theistic probability, which has seven levels between 1 (100% belief in a God) and 7 (100% belief that gods do not exist), Dawkins has said he's a 6.9, which represents a "de facto atheist" who thinks "I cannot know for certain but I think God is very improbable, and I live my life on the assumption that he is not there." When asked about his slight uncertainty, Dawkins quips, "I am agnostic to the extent that I am agnostic about fairies at the bottom of the garden." In May 2014, at the Hay Festival in Wales, Dawkins explained that while he does not believe in the supernatural elements of the Christian faith, he still has nostalgia for the ceremonial side of religion.
Dawkins became a prominent critic of religion and has stated his opposition to religion as twofold: religion is both a source of conflict and a justification for belief without evidence. He considers faith—belief that is not based on evidence—as "one of the world's great evils". He rose to prominence in public debates relating science and religion since the publication of his most popular book The God Delusion in 2006, which became an international best seller. As of 2015, more than three million copies were sold and the book has been translated into over 30 languages. Its success has been seen by many as indicative of a change in the contemporary cultural zeitgeist and has also been identified with the rise of New Atheism. In the book, Dawkins contends that a supernatural creator almost certainly does not exist and that religious faith is a delusion—"a fixed false belief". In his February 2002 TED talk entitled "Militant atheism", Dawkins urged all atheists to openly state their position and to fight the incursion of the church into politics and science. On September 30, 2007, Dawkins, Christopher Hitchens, Sam Harris, and Daniel Dennett met at Hitchens' residence for a private, unmoderated discussion that lasted two hours. The event was videotaped and titled "The Four Horsemen". Dawkins has since been associated with the notion.
Dawkins sees education and consciousness-raising as the primary tools in opposing what he considers to be religious dogma and indoctrination. These tools include the fight against certain stereotypes, and he has adopted the term bright as a way of associating positive public connotations with those who possess a naturalistic worldview. He has given support to the idea of a free thinking school, which would not indoctrinate children in atheism or in any religion but would instead teach children to be critical and open-minded. Inspired by the consciousness-raising successes of feminists in arousing widespread embarrassment at the routine use of "he" instead of "she", Dawkins similarly suggests that phrases such as "Catholic child" and "Muslim child" should be considered as socially absurd as, for instance, "Marxist child", as he believes that children should not be classified based on their parents' ideological or religious beliefs.
Dawkins suggests that atheists should be proud, not apologetic, stressing that atheism is evidence of a healthy, independent mind. He hopes that the more atheists identify themselves, the more the public will become aware of just how many people actually hold these views, thereby reducing the negative opinion of atheism among the religious majority. Inspired by the gay rights movement, he endorsed the Out Campaign to encourage atheists worldwide to declare their stance publicly. He supported the UK's first atheist advertising initiative, the Atheist Bus Campaign in 2008, which aimed to raise funds to place atheist advertisements on buses in the London area.
While some critics, such as writer Christopher Hitchens, psychologist Steven Pinker and Nobel laureates Sir Harold Kroto, James D. Watson and Steven Weinberg have defended Dawkins's stance towards religion and praised his work, others, including Nobel Prize-winning theoretical physicist Peter Higgs, astrophysicist Martin Rees, philosopher of science Michael Ruse, literary critic Terry Eagleton, and theologian Alister McGrath, have criticised Dawkins on various grounds, including the assertion that his work simply serves as an atheist counterpart to religious fundamentalism rather than a productive critique of it, and that he has fundamentally misapprehended the foundations of the theological positions he claims to refute. Rees and Higgs, in particular, have both rejected Dawkins's confrontational stance towards religion as narrow and "embarrassing", with Higgs going as far as to equate Dawkins with the religious fundamentalists he criticises. Atheist philosopher John Gray has denounced Dawkins as an "anti-religious missionary" whose assertions are "in no sense novel or original," suggesting that, "transfixed in wonderment at the workings of his own mind, Dawkins misses much that is of importance in human beings." Gray has also criticised Dawkins's perceived allegiance to Darwin, stating that if "science, for Darwin, was a method of inquiry that enabled him to edge tentatively and humbly toward the truth, for Dawkins, science is an unquestioned view of the world." In response to his critics, Dawkins maintains that theologians are no better than scientists in addressing deep cosmological questions and that he himself is not a fundamentalist as he is willing to change his mind in the face of new evidence.