Carl Sagan

What they got right

He gave ordinary people a practical toolkit for scepticism, the 'baloney detection kit', for testing claims and spotting bad arguments.

Skill it shows

Logical fallacies

Also: Evidence and sources

Try the Baloney Detection Kit

More about Carl Sagan

Carl Sagan was an American astronomer and science communicator, born in 1934, died in 1996. He worked in planetary science and became widely known through the 1980 television series Cosmos, which he wrote with Ann Druyan and Steven Soter, and through the book of the same year. The Demon-Haunted World (1995), parts of it written with Druyan, is his longest lesson in scepticism: the dragon in the garage, and the baloney detection kit in chapter 12. Pale Blue Dot (1994) is the humility he drew from a photograph of Earth. He popularised 'extraordinary claims require extraordinary evidence'. He did not invent the standard. Laplace and Marcello Truzzi are in the note on that card. A sentence a Newsweek reporter wrote about him is filed as misattributed, because affection for the man is not a source.

• Evidence in proportion

  Stranger claims need a stronger case. He also said the extraordinary should still be pursued, which the short form often drops.

• Baloney detection

  A kit in chapter 12 of The Demon-Haunted World: confirmation, debate, distrust of authority, more than one hypothesis, and a test that could fail.

• Wonder and humility

  We are star-stuff, and the Earth is a pale blue dot. Wonder is not a substitute for the kit, and the kit is not a substitute for the scale of the picture.