The Demon-Haunted World

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 infra-red 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.

Sagan presents a set of tools for skeptical thinking that he calls the "baloney detection kit".[2][3]^:210[4] 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.

There are a total of nine tools in this kit. The first of these tools that Sagan provides is that there must be confirmation of the facts given when possible. The next tool in the "baloney detection kit" is to encourage debate on the evidence from all points of view. The next tool is that we must 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. The fourth tool in the kit is to 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. The fifth tool in the kit is to try your best to not purely stick to a hypothesis that is your own and become bias. Sagan tells us to compare our own hypothesis with others to see if we can find reasons to reject our own hypothesis. The next tool in the kit is to 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. The next tool is that we must know that if there is a chain of argument, every link in that chain must be correct. The eighth and possibly most important tool in the "baloney detection kit" is the use of Occam's Razor, which tells us to choose the hypothesis that is simpler and requires the least amount of assumptions. The final tool in the kit is to always 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. With the use of this "baloney detection kit" it is easier to critically think and find the truth.

There is a second part to the kit that Sagan gives us. This consists of twenty different logical fallacies that one must not commit when offering up a new claim. The first of these fallacies is ad hominem which is when an arguer attacks the opposing arguer and not the actual argument. Next is the argument from authority which is when someone expects another to immediately believe that a person of authority or higher knowledge is correct. The third fallacy that Sagan gives us is the argument from adverse consequences. This is when someone says that something must be done a certain way or else there will be adverse consequences. The next fallacy is the appeal to ignorance. This is when one argues a claim in that whatever has not been proved false must be true, and vice versa. Next Sagan tells us not to commit special pleading. This is when 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". The next fallacy is known as begging the question. This is when 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. The next fallacy Sagan gives us is called observational selection. This is when 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. The next fallacy, as Sagan calls it, is statistics of small numbers. This is when someone argues something by giving the statistics in small numbers, which isn't very reliable. Next is the fallacy called misunderstanding of the nature of statistics. This is when, as you would assume, someone misinterprets statistics given to them. Next is the fallacy of inconsistency. This is when, as you would also assume, an arguer is very inconsistent in their claims. The next fallacy is non sequitur. This is Latin for "it doesn't follow". This fallacy is committed when a claim is made that doesn't make much sense, such as "Our nation will prevail because God is great". The next fallacy Sagan discusses is called post hoc ergo propter hoc, Latin for "it happened after, so it was caused by." This fallacy is committed when an arguer claims that something happened because of a past event when really it probably didn't. The next fallacy is known as a meaningless question. This fallacy is committed when someone asks a question that has no real meaning or doesn't add to the argument at all. Sagan also discusses a fallacy known as the excluded middle. This fallacy is committed when an arguer only considers or mentions the two opposite extremes of the conversation and excludes the aspects in between the two extremes.

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.

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.[2]

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.

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.

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 alien 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.”[5] Ingram was eventually able to have a foggy visualization of the claimed events, and he suggested that perhaps “a demon might be responsible.”[5] 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.”[5]