Carl Sagan gave the public a baloney detection kit

Person: Carl Sagan
Lived: 1934–1996
Field: Astronomy, planetary science
From: American

The story

Carl Sagan loved wonder, but he insisted that wonder must be paired with scepticism. He credited Martin Gardner's Fads and Fallacies in the Name of Science and Charles Mackay's Extraordinary Popular Delusions and the Madness of Crowds with teaching him to think critically. Throughout his career he challenged astrology, crystal healing and other pseudoscience, and in 1974 he challenged Immanuel Velikovsky to a public debate. He often lamented that most newspapers ran a daily astrology column while very few offered even a weekly column on astronomy.

The phrase that became his best-known tool came from a dinner conversation. Arthur Felberbaum, a friend of Sagan's wife Ann Druyan, told Sagan he dreamed that everyone could carry a baloney detection kit in their head. Sagan took up the idea in a 1987 column for Parade magazine, The Fine Art of Baloney Detection, and expanded it in his penultimate book, The Demon-Haunted World: Science as a Candle in the Dark (1995), four of whose 25 chapters he wrote with Druyan.

The kit has two parts. The first is a set of habits for testing a claim: seek independent confirmation of the facts, encourage debate, think of more than one explanation, avoid becoming attached to your own hypothesis, quantify wherever possible, prefer the simpler explanation, and ask whether the idea could ever be shown to be false. The second part lists common traps in reasoning, such as arguing from authority, appealing to ignorance, relying on statistics from tiny samples and attacking a straw man. Sagan illustrated the problem of untestable claims with a memorable story about an invisible, floating, fire-breathing dragon in his garage that defeats every test a visitor proposes.

Sagan also made famous the maxim that “extraordinary claims require extraordinary evidence,” sometimes called the Sagan standard. It echoed a similar statement by his fellow sceptic Marcello Truzzi and an older principle traced to the French scientist Pierre-Simon Laplace. Sagan argued that science is more than a body of knowledge: it is a way of thinking, with a built-in mechanism for correcting its own errors.

The Demon-Haunted World became a New York Times bestseller and won the 1996 Los Angeles Times Book Prize in science and technology. The modern sceptical movement regards it as an important book, and the baloney detection kit is still offered to students and general readers as a practical checklist for judging the claims they read and hear.

Why it matters

Sagan's baloney detection kit gave ordinary readers a simple, memorable checklist for weighing evidence, and it is still widely used to teach critical thinking in an age of misinformation.

About Carl Sagan

Brooklyn-born astronomer who explained the Venus greenhouse, helped send humanity’s messages on Pioneer and Voyager, and taught Cosmos viewers worldwide to look at the universe with wonder and doubt.

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Carl Sagan

1934–1996 · Astronomy, planetary science

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