Atheism is the absence of a belief in god(s).
The Cigarette Smoking Man admits to being an atheist in the episode Requiem during a discussion with Marita Covarrubias. Expressing his desire to know the aliens' plans, he tells Marita it would help understand everything about the universe, to which she asks if he means God. The man replies: "There is no God, Marita. Everything we call God is only alien."
Behind the scenes
- William B. Davis, the actor who played the Cigarette Smoking Man, is an atheist himself, and considers prominent atheist Richard Dawkins his hero - although Dawkins has condemned the X-Files for promoting paranormal thinking and denying critical thought.