November 9: Fermi and the ‘Great’ General
On this day in 1934, astronomer and Pulitzer Prize winning author Carl Sagan was born. Sagan’s talent and enthusiasm for describing the stars made him America’s best known scientist. His public television series “Cosmos” was one of the most widely viewed series in television history, challenging viewers to contemplate the vastness of the universe and the possibility of life existing elsewhere in the universe.
In Sagan’s posthumously published book The Demon-Haunted World: Science as a Candle in the Dark (1997), he challenges readers to explore the universe of their mind. In a chapter called “The Fine Art of Baloney Detection,” Sagan explores the dos and the don’ts of sound, skeptical thinking. In the tradition of the scientific method, Sagan challenges the reader to have at the ready the following principles for detecting nonsense in any argument:
1. Do an independent confirmation of the facts.
2. Debate the argument, seeking all points of view.
3. Spin more than one hypothesis by seeking out other possible explanations and disconfirming evidence.
4. Fight against the instinct toward confirmation bias by keeping an open mind.
5. Look for quantifying evidence, numerical data, that supports the argument.
6. Examine your line of reasoning, checking to make sure that every link in the chain of argument is sound.
7. Use Occam’s Razor as a rule of thumb when examining alternative hypotheses.
8. Test your hypothesis. Think like a scientist to determine how a skeptic might approach your argument. Just as a science experiment can be duplicated, would your conclusions hold up under scrutiny?
To illustrate the scientist’s skeptical mindset, Sagan shared an anecdote about the Italian physicist Enrico Fermi, who emigrated to America during World War II to work on the Manhattan project. On the way to meet one of the leaders he would be working with on the government project, Fermi’s companion told him that the man they were about to meet was a “great general.” Fermi immediately challenged the claim with some questions:
What is the definition of a great general? Fermi characteristically asked. I guess it’s a general who’s won many consecutive battles. How many? After some back and forth, they settled on five. What fraction of American generals are great? After some more back and forth, they settled on a few percent.
Fermi challenged his companion to question the hypothesis and to consider an alternative one: that there is no such thing as a great general. This would mean that the winning or losing of battles would be left to chance. Quantifying the argument would make the chances of winning a single battle one out of two, “or ½, two battles ¼, three ⅛, four 1/16, and five consecutive battles 1/32 — which is about 3 percent.” Based on these numbers, it is possible that an American general might by chance win five consecutive battles. Fermi concluded with another question: “Now, has any of them won ten consecutive battles . . .?” (1).
Since Sagan’s death in 1996 at the age of 62, the amount of baloney in our world has grown exponentially. More than ever, we need to keep in mind Sagan’s principles of baloney detection, and always be ready, like Fermi was, to apply them as a means to being scrupulously skeptical.