Suppose the coinage of a country has a portrait of one of its eminent sovereigns on one side and a specimen of its magnificent fauna on the other. Now consider a simple if-then rule: “If a coin has a king on one side, then it has a bird on the other.” Here are four coins, displaying a king, a queen, a moose, and a duck. Which of the coins do you have to turn over to determine whether the rule has been violated?

Answer: If you’re like most people, you said “the king” or “the king and the duck.” The correct answer is “the king and the moose.” Why? Everyone agrees you have to turn over the king, because if you failed to find a bird on the reverse it would violate the rule in so many words. Most people know there’s no point in turning over the queen, because the rule says “If king, then bird”; it says nothing about coins with a queen. Many say you should turn over the duck, but when you think about it, that coin is irrelevant. The rule is “If king, then bird,” not “If bird, then king”: if the duck shared the coin with a queen, nothing would be amiss. But now consider the moose. If you turned that coin over and found a king on the obverse, the rule “If king, then bird” would have been transgressed. The answer, then, is “the king and the moose.”

— Steven Pinker, Rationality

• A smartphone and a case cost $110 in total. The phone costs $100 more than the case. How much does the case cost?
• It takes 8 printers 8 minutes to print 8 brochures. How long would it take 24 printers to print 24 brochures?
• On a field there is a patch of weeds. Every day the patch doubles in size. It takes 30 days for the patch to cover the whole field. How long did it take for the patch to cover half the field? The economist Shane Frederick gave these questions (with different examples) to thousands of university students. Five out of six got at least one of them wrong; one in three got them all wrong.

Answers:

• $5
• 8 minutes
• 29 days

— Steven Pinker, Rationality

To make discoveries in science, both small and important, you must be an expert on the topic addressed. To be an expert innovator requires commitment. Commitment to a subject implies sustained hard work.

— Edward O. Wilson, Letters to a Young Scientist

The curse of modernity is that we are increasingly populated by a class of people who are better at explaining than understanding…

— Nassim Nicholas Taleb, Skin in the Game

That Douglass and King could approvingly quote Jefferson, himself a hypocritical and in some ways dishonorable man, does not compromise the rationality of their arguments but reinforces it. We should care about people’s virtue when considering them as friends, but not when considering the ideas they voice. Ideas are true or false, consistent or contradictory, conducive to human welfare or not, regardless of who thinks them.

— Steven Pinker, Rationality