Carl Sagan – A Humanist You Should Know

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poster version of Carl SaganNovember 9th is the birthday of Carl Sagan (1934-1996), an American astronomer, astrophysicist, cosmologist, author, science popularizer, and science communicator in astronomy and other natural sciences. He is best known as creator and host of the seminal science TV show Cosmos: A Personal Voyage (1980). Sagan was known as a skeptic and freethinker. That is why today is considered Carl Sagan Day by many in the freethought community.

The Center for Inquiry and especially our sister organization, the Committee for Skeptical Inquiry, had the honor of working with Dr. Sagan for twenty years, from 1976, when he was one of the founding members of CSI (then known as CSICOP), to 1996, when he published the last of his many articles in Skeptical Inquirer, just months before he died.

In 2009, CFI Ft. Lauderdale, FLASH and other groups created the first Carl Sagan Day celebration for his birthday, November 9th, and the idea quickly spread around the world. Now groups from Australia to Alaska are planning star parties, astronomy lectures, science fairs, teacher workshops and more to say thanks to Dr. Sagan and bring his work to the next generation of “star stuff.”

Carl Sagan Day

Besides Cosmos, Sagan is also known in the freethought community for his “baloney detection kit” that he described in his 1995 book “The Demon-Haunted World: Science as a Candle in the Dark“:

  • Wherever possible there must be independent confirmation of the “facts.”
  • Encourage substantive debate on the evidence by knowledgeable proponents of all points of view.
  • Arguments from authority carry little weight — “authorities” have made mistakes in the past. They will do so again in the future. Perhaps a better way to say it is that in science there are no authorities; at most, there are experts.
  • Spin more than one hypothesis. If there’s something to be explained, think of all the different ways in which it could be explained. Then think of tests by which you might systematically disprove each of the alternatives. What survives, the hypothesis that resists disproof in this Darwinian selection among “multiple working hypotheses,” has a much better chance of being the right answer than if you had simply run with the first idea that caught your fancy.
  • Try not to get overly attached to a hypothesis just because it’s yours. It’s only a way station in the pursuit of knowledge. Ask yourself why you like the idea. Compare it fairly with the alternatives. See if you can find reasons for rejecting it. If you don’t, others will.
  • Quantify. If whatever it is you’re explaining has some measure, some numerical quantity attached to it, you’ll be much better able to discriminate among competing hypotheses. What is vague and qualitative is open to many explanations. Of course there are truths to be sought in the many qualitative issues we are obliged to confront, but finding them is more challenging.
  • If there’s a chain of argument, every link in the chain must work (including the premise) — not just most of them.
  • Occam’s Razor. This convenient rule-of-thumb urges us when faced with two hypotheses that explain the data equally well to choose the simpler.
  • Always ask whether the hypothesis can be, at least in principle, falsified. Propositions that are untestable, unfalsifiable are not worth much. Consider the grand idea that our Universe and everything in it is just an elementary particle — an electron, say — in a much bigger Cosmos. But if we can never acquire information from outside our Universe, is not the idea incapable of disproof? You must be able to check assertions out. Inveterate skeptics must be given the chance to follow your reasoning, to duplicate your experiments and see if they get the same result.
  • Carl Sagan was the Neil deGrasse Tyson of his day.

    “Extraordinary claims require extraordinary evidence” – Carl Sagan

    Extra LinkAudio of Dr. Sagan’s Humanist of the Year speech at the 1981 American Humanist Association Conference in San Diego, California.


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