The Demon-Haunted World by Carl Sagan - Book Report

Carl Sagan was an American astrophysicist, best known as a science popularizer and the narrator and co-writer 

of the TV show Cosmos, and he was also an advocate for scientific skepticism. His 1995 book The Demon-

Haunted World continues his cause by introducing the reader to a variety of pseudoscientific and paranormal 

topics and providing more reasonable and scientific answers to the phenomena. Sagan also goes into some of 

the history of science, explaining how we reached our current understandings. Maybe most importantly, he 

advocates for the appreciation of science. While many are drawn to pseudoscience and the paranormal because 

they are wondrous and exciting, Sagan would argue that science is the true source of wonder and excitement. 

 Since most of Sagan’s academic research was in astrobiology, it makes sense that he devotes a lot of time to 

discussing aliens. He starts with the “Man in the Moon” and the “Face on Mars”. Many civilizations have

claimed to see patterns in the sky, including constellations and a face on the surface of the moon. Sagan 

describes how humans are a “gregarious lot” and that “the pattern-recognition machinery in our brains is so 

efficient in extracting a face from a clutter of other detail that we sometimes see faces where there are none.” 

The pictures of the surface of Mars from the Viking landers received a similar treatment. There are formations 

that resemble Egyptian pyramids or human faces, but it is enough to say that people seek these patterns. Since 

there were about 100,000 pictures taken, it would be more surprising if no one saw any patterns in the rocks. 

Sagan then goes over some other aspects of aliens, including: crop circles, which people have admitted to 

creating; UFO sightings, which can be explained by the sightings’ proximity to military bases; and abductions, 

which can be explained by either sleep paralysis, hallucinations, or credulous or dishonest therapists. I think 

the historical parallel with alien abductions is the most interesting. In the Middle Ages, people believed they 

were visited by demons or fairies or spirits in their sleep, but now people believe they are visited by aliens. 

The creature is based on the culture, but humans still have the same psychology.

As a thought experiment to demonstrate the importance of falsifiability in science, Sagan supposes that a fire-

breathing dragon lives in his garage. This should be easy to verify by looking in his garage, but he claims that 

it is invisible. Moreover, it floats, its fire is heatless, and it is, in fact, incorporeal. There is no way to detect it, 

and it has no physical influence on anything. What then, Sagan asks, is the difference between this dragon and 

nothing at all? He ties this in with aliens and the evidence that people claim to have, but I think this framework 

should be applied to many things, including religion. 

When people study a science, for example physics, they are not required to independently derive Maxwell’s 

equations or the Schrodinger equation every time they are asked to solve a problem, or even the first time. We 

take knowledge from the people before us, so that we can advance further. Sagan then describes the !Kung 

people of the Kalahari Desert. They are hunter-gatherers, but their method of tracking resembles the science 

used in the rest of the world. They analyze footprints the same way modern astronomers analyze craters, they 

use the movement of the sun to deduce the age of tracks, since animals tend to seek the shade of trees, and so 

on. The !Kung do not consult the stars or examine the guts of a sacrifice before going hunting. They use reason 

and knowledge passed down through generations, just as modern scientists do. This chapter is part of the 

section of the book where Sagan talks about the awful scientific literacy rates in America. He attributes a lot of 

it to how science is presented to kids. There are few educational TV shows, Sagan says, and having more 

might improve scientific literacy. This book was informed by the state of media in 1995, so maybe now the 

Internet would be a better place to advance scientific literacy.  

While Sagan brings up a decent variety of pseudoscientific and paranormal ideas to debunk, I think he 

sometimes focuses on aliens too much, to the point where he repeats himself. As a skeptical person, there was 

very little that Sagan said that I disagree with, but I did enjoy learning about all the examples he gave, 

especially the demon-alien parallel and the !Kung people. For the skeptics, I would recommend this book as a 

collection of interesting examples and counterarguments, and for the nonskeptics, I would recommend this 

book even more, since I believe its messages are important.