The Demon-Haunted World

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The Demon-Haunted World: Science as a Candle in the Dark
Cover of the first edition
AuthorCarl Sagan
CountryUnited States
SubjectsScientific skepticism
PublisherRandom House
Publication date
Media typePrint (hardcover and paperback)
001.9 20
LC ClassQ175 .S215 1995
Preceded byPale Blue Dot 
Followed byBillions and Billions 

The Demon-Haunted World: Science as a Candle in the Dark is a 1995 book by the astrophysicist Carl Sagan. (Four of the 25 chapters were written with Ann Druyan).[1]: x  In it, Sagan aims to explain the scientific method to laypeople and to encourage people to learn critical and skeptical thinking. He explains methods to help distinguish between ideas that are considered valid science and those that can be considered pseudoscience. 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 explains that science is not just a body of knowledge, but is a way of thinking. 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. He says that science works much better than any other system because it has a "built-in error-correcting machine".[2]: 27  Superstition and pseudoscience get in the way of the ability of many laypersons to appreciate the beauty and benefits of science. Skeptical thinking allows people to construct, understand, reason, and recognize valid and invalid arguments. Wherever possible, there must be independent validation of the concepts whose truth should be proved. He states that reason and logic would succeed once the truth were known. Conclusions emerge from premises, and the acceptability of the premises should not be discounted or accepted because of bias.

Dragon in my garage[edit]

As an example of skeptical thinking, Sagan offers a story concerning a fire-breathing dragon who lives in his garage. When he persuades a rational, open-minded visitor to meet the dragon, the visitor remarks that they are unable to see the creature. Sagan replies that he "neglected to mention that she's an invisible dragon". 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". When the visitor considers using an infrared camera to view the creature's invisible fire, Sagan explains that her fire is heatless. He continues to counter every proposed physical test with a reason why the test will not work.

Sagan concludes by asking: "Now what's the difference between an invisible, incorporeal, floating dragon who spits heatless fire and no dragon at all? If there's no way to disprove my contention, no conceivable experiment that would count against it, what does it mean to say that my dragon exists? Your inability to invalidate my hypothesis is not at all the same thing as proving it true."

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.

Baloney detection kit[edit]

Sagan presents a set of tools for skeptical thinking that he calls the "baloney detection kit".[3][4]: 210 [5] Skeptical thinking consists both of constructing a reasoned argument and recognizing a fallacious or fraudulent one. 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's "baloney detection kit" also provides tools for detecting "the most common fallacies of logic and rhetoric", such as argument from authority and statistics of small numbers. Through these tools, Sagan argues the benefits of a critical mind and the self-correcting nature of science can take place.

Sagan provides nine tools as the first part of this kit.

  1. There must be independent confirmation of the facts given when possible.
  2. Encourage debate on the evidence from all points of view.
  3. Realize that an argument from authority is not always reliable. Sagan supports this by telling us that 'authorities" have made mistakes in the past and they will again in the future.
  4. Consider more than one hypothesis. Sagan adds to this by telling us that we must think of the argument from all angles and think all the ways it can be explained or disproved. The hypothesis that then still hasn't been disproved has a much higher chance of being correct.
  5. Try your best to not purely stick to a hypothesis that is your own and become biased. Sagan tells us to compare our own hypothesis with others to see if we can find reasons to reject our own hypothesis.
  6. Quantify. Sagan tells us that if whatever we are trying to explain has numerical value or quantitative data related to it, then we'll be much more able to compete against other hypotheses.
  7. If there is a chain of argument, every link in that chain must be correct.
  8. The use of Occam's razor, which tells us to choose the hypothesis that is simpler and requires the least amount of assumptions.
  9. Ask if a given hypothesis can be falsified. Sagan tells us that if a hypothesis cannot be tested or falsified then it is not worth considering.

Sagan suggests that with the use of this "baloney detection kit" it is easier to critically think and find the truth.

Logical fallacies[edit]

There is a second part to the kit. This consists of twenty logical fallacies that one must not commit when offering up a new claim.

  1. Ad hominem. An arguer attacks the opposing arguer and not the actual argument.
  2. Argument from authority. Someone expects another to immediately believe that a person of authority or higher knowledge is correct.
  3. Argument from adverse consequences. Someone says that something must be done a certain way or else there will be adverse consequences.
  4. Appeal to ignorance. One argues a claim in that whatever has not been proved false must be true, and vice versa.
  5. Special pleading. An arguer responds to a deeply complex or rhetorical question or statement by, usually, saying "oh you don't understand how so and so works."
  6. Begging the question. An arguer assumes the answer and makes a claim such as, this happened because of that, or, this needs to happen in order for that to happen.
  7. Observational selection. Someone talks about how great something is by explaining all of the positive aspects of it while purposely not mentioning any of the negative aspects.
  8. Statistics of small numbers. Someone argues something by giving the statistics in small numbers, which isn't very reliable.
  9. Misunderstanding of the nature of statistics. Someone misinterprets statistics given to them.
  10. Fallacy of inconsistency. An arguer is very inconsistent in their claims.
  11. Non sequitur. This is Latin for "it doesn't follow." A claim is made that doesn't make much sense, such as "Our nation will prevail because God is great."
  12. Post hoc ergo propter hoc. Latin for "it happened after, so it was caused by." An arguer claims that something happened because of a past event when really it probably didn't.
  13. Meaningless question. Someone asks a question that has no real meaning or doesn't add to the argument at all.
  14. The excluded middle. An arguer only considers or mentions the two opposite extremes of the conversation and excludes the aspects in between the two extremes.
  15. Short-term vs. long-term. A subset of the excluded middle, but so important it was pulled it out for special attention.
  16. Slippery slope, related to excluded middle (e.g., If we allow abortion in the first weeks of pregnancy, it will be impossible to prevent the killing of a full-term infant. Or, conversely: If the state prohibits…)
  17. Confusion of correlation and causation. The latter causes the former
  18. Straw man. Caricaturing a position to make it easier to attack. This is also a short-term/long-term fallacy
  19. Suppressed evidence, or half-truth.
  20. Weasel word. Talleyrand said: "An important art of politicians is to find new names for institutions which under old names have become odious to the public." 

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. He is critical of organized religion.[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. It actually came from a friend of mine named Arthur Felberbaum who died about forty years ago. He and Carl and I once sat down for dinner together. His politics were very left wing, so Carl and Arthur and I were trying to find common ground so that we could have a really good dinner together. And at one point, Arthur said, "Carl, it's just that I dream that every one of us would have a baloney detection kit in our head." And that's where that idea came from.[3]

Misuse of science[edit]

Sagan indicates that science can be misused. Thus, he is highly critical of Edward Teller, the "father of the hydrogen bomb", and Teller's influence on politics, and contrasts his stance to that of Linus Pauling and other scientists who took moral positions.[citation needed]

Sagan also discusses the misuse of science in representation. He relates to the depiction of the mad scientist character in children's TV shows and is critical of this occurrence. Sagan suggests an addition of scientific television programs, many of which would take a look at believed hoaxes of the past and encourage viewers to engage in critical thinking to better represent science on popular Television.

Misuse of psychiatric authority[edit]

Sagan indicates that therapists can contribute to the growth of pseudoscience or the infusion of "false stories". He is critical of John Mack and his support of abduction cases, which were represented in his patients.

Sagan writes about the story of Paul Ingram. Ingram's daughter reported that her father had sexually abused her. He was told that "sex offenders often repressed memories of their crimes."[6] Ingram was eventually able to have a foggy visualization of the claimed events, and he suggested that perhaps "a demon might be responsible."[6] Sagan describes how once Ingram started remembering events, so did several other individuals and family members. A "memory recovery" technique was performed on Ingram, and he confessed to the crimes. A medical examination was done on his daughter, where none of the scars she described were actually found. Sagan writes that Ingram later tried to plead innocence once "away from his daughters, his police colleagues, and his pastor."[6]


Hoaxes have played a valuable role in the history of science by revealing the flaws in our thinking and helping us advance our critical thinking skills. One of Sagan’s examples is the "Carlos hoax" by James Randi that revealed flaws in reporting by news media. Carlos was described as an ancient spirit that supposedly possessed José Alvarez and provided Alvarez with advanced knowledge about the universe. Many news outlets assumed this was true and reported it as such, which spread misinformation.

Sagan also cites crop circles as hoaxes.

Reception and legacy[edit]

The book was a New York Times bestseller.[7] The contemporary skeptical movement considers it an important book.[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. One such issue is consequences of pouring governmental money into cancer research. Trachtman writes, "it is not because of such beliefs that Congress now approaches the NIH budget with an ax. In fact, billions of dollars spent on years of research in the war on cancer have spawned growing professional bureaucracies and diminishing medical benefits."[12] Trachtman argues that Sagan does not include problems like growing bureaucracies and diminishing medical benefits as reasons for a lack of scientific attention. In his review for the New York Times, James Gorman also argues for an unaddressed issue in Sagan's book, saying Sagan fails to emphasize the idea that scientists should take a more active role in reaching science to the public, while he does mention the failures of the education system to do so.[13]

The review in the Smithsonian magazine and a review in the New York Review of Books provide a range of opinions on Sagan's attitude towards religious ideas. Per the New York Review article, "when it comes to the Supreme Extraterrestrial he is rather circumspect."[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." The Smithsonian goes on to say that Sagan's defined religious views fall within the area of an untestable claim, a type of claim he argues against in The Demon-Haunted World.[12]

The article in the New York Review also claims that Sagan includes something in The Demon-Haunted World which he also is arguing against in that same text. The article mentions how Sagan discusses a natural predisposition people have towards science; but, the article says, "He does not tell us how he used the scientific method to discover the "embedded" human proclivity for science."[14] Sagan heavily discusses the importance of using the scientific method in his book, and this article claims he strays away from his own message by not including a description of his use of the scientific method on this topic.

An article in the Los Angeles Times describe Sagan's book positively. The Los Angeles Times describes Sagan's book as "a manifesto for clear thought", with the main issue being the length of eight chapters.[15] This lengthy discussion is also addressed in the archived New York Times article,[16] which relates to the book as having areas which repeat themselves.

The Demon-Haunted World has been defined in more current sources as still relevant. An article in The Guardian, 2012, suggests the still current relevance of The Demon-Haunted World.[17] Another article from The Verge in 2017 also supports this relevance.[18] The latter article mentions a disconnect between what is proven by science to be the best answer and what is chosen to be done by governmental bodies.[19] Carl Sagan covers this concept as a prominent issue in his book (1995), and this article outlines it as a problem still occurring in 2017.


The Demon-Haunted World provides many arguments about our society that will always remain relevant. Sagan mainly argues for increased education among younger populations regarding critical thinking and scientific literacy. First, he explains that scientific literacy and critical thinking are essential for democracy, especially in the United States. Democracy allows people to share their beliefs, but with this come many different perspectives and arguments. Critical thinking is required to determine which are true or false. Scientific literacy provides similar tools and benefits to critical thinking; Sagan asserts science allows us to participate in the most significant method of understanding our Universe. Science is constantly evolving and is intertwined with our democracy, so to fully participate in democracy, you must be able to understand science. Sagan explains that science can be used to escape poverty, aid us in determining how to preserve our world, and to understand our origin and place in the Universe, “Without science and democracy, we risk being a nation of suckers.”[20] Science can also be a valuable tool in examining a community’s social, political, and economic systems to reveal flaws and provide methods of improvement. Sagan asserts all individuals should have the ability to recognize errors.

Sagan insists that "there are no stupid questions" because asking questions is how we advance scientific knowledge. Denying that any questions are stupid also encourages children to develop critical thinking skills. Some examples Sagan provides include “Why is the grass green?” and “Why do we have toes?”[21] Both of these help answer questions about biology, evolution, and the human body. Discouraging anyone from asking these questions and instead just accepting that these are facts of life may contribute to flaws in thinking patterns in the future. Being used to accepting the way things are just because is exactly what Sagan is attempting to fix, encouraging everyone to remain skeptical and question everything. He also places emphasis on using the “Baloney Detection Kit” to spot flaws (see above).

In the decade or so prior to the publication of The Demon-Haunted World, alien abduction accounts were common. Sagan provides concrete examples for why we shouldn’t assume things are true and instead use tools such as Occam's razor to seek more reasonable, science-based explanations.

See also[edit]


  1. ^ Sagan, Carl (1997). The Demon-Haunted World: Science As a Candle in the Dark (Reprint ed.). Ballantine Books. ISBN 978-0345409461.
  2. ^ Sagan, Carl (1997). The Demon-Haunted World: Science As a Candle in the Dark (Reprint ed.). Ballantine Books. ISBN 978-0345409461.
  3. ^ a b Palmer, Rob (March 31, 2020). "Exploring 'Possible Worlds' With Ann Druyan". CFI. Archived from the original on April 1, 2020. Retrieved April 17, 2020.
  4. ^ Sagan, Carl (March 1997). The Demon-Haunted World: Science As a Candle in the Dark (Paperback ed.). Ballantine Books. ISBN 978-0-345-40946-1.
  5. ^ Sagan, Carl (1995). The Demon-Haunted World: Science As a Candle in the Dark (Hardback ed.). Random House. ISBN 978-0-394-53512-8.
  6. ^ a b c Carl Sagan,(1997). The Demon-Haunted World: Science As a Candle in the Dark (Reprint ed.). Ballantine Books. ISBN 978-0345409461.
  7. ^ "Best Sellers". The New York Times. June 16, 1996. Retrieved February 17, 2017.
  8. ^ Bernstein, Evan (November 9, 2015). "Happy Carl Sagan Day!". The Skeptics' Guide to the Universe. Retrieved February 17, 2017.
  9. ^ Novella, Steven (November 9, 2009). "NeuroLogica Blog » Carl Sagan Day". New England Skeptical Society. Retrieved February 17, 2017.
  10. ^ Meadon, Michael (October 8, 2009). "Books IV". Retrieved February 17, 2017.
  11. ^ Swiss, Jamy Ian (May 9, 2013). "I, Skeptic". Northeast Conference on Science and Skepticism. Retrieved February 17, 2017 – via YouTube.
  12. ^ a b Trachtman, Paul (May 1997). "Review of 'The Demon-Haunted World', 'Einstein, History, and Other Passions', 'The End of Science'". Smithsonian. Archived from the original on September 27, 2009.
  13. ^ The New York Times,
  14. ^ a b Lewontin, Richard C. "Billions and Billions of Demons." The New York Review of Books, 27 Aug. 2020,
  15. ^ "Book Review / Non Fiction  : For This Scientist, the Truth Is Out There: The Demon-Haunted World: Science as a Candle in the Dark by Carl Sagan; Random House $25, 452 Pages." Los Angeles Times, 18 Apr. 1996,
  16. ^ The New York Times, The New York Times,
  17. ^ "The Demon-Haunted World by Carl Sagan – Review | Tim Radford." The Guardian, Guardian News and Media, 20 July 2012,
  18. ^ Savov, Vlad. "The World Needs Carl Sagan Now More than Ever." The Verge, The Verge, 24 Jan. 2017,
  19. ^ Savov, Vlad. "The World Needs Carl Sagan Now More than Ever." The Verge, The Verge, 24 Jan. 2017,
  20. ^ Sagan, Carl (1995), p. 38. The Demon-Haunted World: Science As a Candle in the Dark (Hardback ed.). Random House. ISBN 978-0-394-53512-8.
  21. ^ Sagan, Carl (1995), p. 323. The Demon-Haunted World: Science As a Candle in the Dark (Hardback ed.). Random House. ISBN 978-0-394-53512-8.

Further reading[edit]