The title comes from the fact that the Pirahas don't have a word for goodnight – their nearest equivalent when they are leaving someone for the night is Don't Sleep, There Are Snakes. Daniel Everett also uncovered interesting information about the lack of words for colors in this society. However, he hits a wall when trying to convince them to convert, and he goes into the irreconcilable differences between cultures.

His perplexing objective was “to convince happy, satisfied people that they are lost and need Jesus as their personal savior. Someone like me, who has a Western worldview, finds it hard to imagine living life without say, counting and numbers. Everett states in his book that he as well as a series of psychologists completed experiments to prove that the Pirahas had no words for numbers in their culture. Everett pleads with the captain of the boat they’ve hitched a lift on, to hurry to the port where they can get to hospital. However, it's very difficult to accept that argument from someone who doesn't even really know if he speaks the language correctly.This is much less dry than it sounds, and is all cunningly tied into an equally fascinating story of Everett’s life with the Piraha and his loss of faith. His family is mentioned briefly, and, in almost every instance, in situations framed where his wife and children are in danger and sitting passively by, while Everett is rescuing them in a rather macho fashion. By the late ‘80s, after ten years of failed efforts, Everett realized that he had become a closet atheist.

Everett found himself more and more persuaded that “the act of believing in something unseen” was ridiculous. I don't think many people living with a smartphone in their pocket would, given the choice, give up their lives, move to the jungle and spend all day hunting, gathering and making sure they're not killed by a wild animal. But the bulk of the text is devoted to really trying to understand their culture, which he does through the “immediacy of experience” principle.Then, his stepmother committed suicide, he saw the light, accepted Jesus, and his life became better.