[1]: x In it, Sagan aims to explain the scientific method to laypeople and to encourage people to learn critical and skeptical thinking.
Sagan states that when new ideas are offered for consideration, they should be tested by means of skeptical thinking and should stand up to rigorous questioning.
Sagan shows how scientific thinking is both imaginative and disciplined, bringing humans to an understanding of how the universe is, rather than how they wish to perceive it.
The visitor suggests spreading flour on the floor so that the creature's footprints might be seen, which Sagan says is a good idea, "but this dragon floats in the air".
Continuing with concepts relevant to the 'dragon in my garage' story, Sagan writes about a patient of John Mack who claimed to have scars on her body which were from encounters with aliens.
Sagan writes that if the patient is asked what her scars look like, she is unable to show them because, unfortunately, they are located in the private areas of her body.
In order to identify a fallacious argument, Sagan suggests employing such tools as independent confirmation of facts, debate, development of different hypotheses, quantification, the use of Occam's razor, and the possibility of falsification.
Sagan provides a skeptical analysis of several examples of what he refers to as superstition, fraud, and pseudoscience such as witches, UFOs, ESP, and faith healing.
[citation needed] In a 2020 interview for Skeptical Inquirer, when Sagan's wife Ann Druyan was asked about the origin of the phrase "baloney detection kit", she said that It didn't really come from Carl.
One of Sagan's examples is the "Carlos hoax" by James Randi that revealed flaws in reporting by news media.
[8][9][10][11] The Demon-Haunted World has been criticized (in Smithsonian magazine and The New York Times) for not incorporating certain information relevant to the items he discusses in his book.
The Smithsonian article by Paul Trachtman argues that Sagan relates issues of government choices and declining scientific thinking skills to pseudoscience topics like astrology and faith healing but ignores other issues that may be causing governmental bodies and other individuals to turn away from science.
In fact, billions of dollars spent on years of research in the war on cancer have spawned growing professional bureaucracies and diminishing medical benefits."
Trachtman argues that Sagan does not include problems like growing bureaucracies and diminishing medical benefits as reasons for a lack of scientific attention.
"[14] The Smithsonian article suggests Sagan was very clear about his religious beliefs in the book, for he "splits his universe in two, into science and irrationality."
It described Sagan's book as "a manifesto for clear thought", with the main issue being the length of eight chapters.
The article praised the book, stating that Sagan "practiced the scientific skepticism and thinking that he preached, and that's what helped him accurately analyze the trends of his time and forecast their eventual outcomes in ours.".