Rationality: What It Is, Why It Seems Scarce, Why It Matters

by Steven Pinker

(The Wikipedia entry for cognitive biases lists almost two hundred.)

we can understand human nature only by considering the mismatch between the environment in which we evolved and the environment we find ourselves in today.

Just as citizens should grasp the basics of history, science, and the written word, they should command the intellectual tools of sound reasoning. These include logic, critical thinking, probability, correlation and causation, the optimal ways to adjust our beliefs and commit to decisions with uncertain evidence, and the yardsticks for making rational choices alone and with others.

Many act as if rationality is obsolete—as if the point of argumentation is to discredit one’s adversaries rather than collectively reason our way to the most defensible beliefs.

A MAJOR THEME of this book is that none of us, thinking alone, is rational enough to consistently come to sound conclusions: rationality emerges from a community of reasoners who spot each other’s fallacies.

our three most conspicuous traits: our two-leggedness, which enables us to run efficiently; our hairlessness, which enables us to dump heat in hot climates; and our big heads, which enable us to be rational.

Three quarters of Americans believe in at least one phenomenon that defies the laws of science, including psychic healing (55 percent), extrasensory perception (41 percent), haunted houses (37 percent), and ghosts (32 percent)—which also means that some people believe in houses haunted by ghosts without believing in ghosts.

Echoing a famous argument by the philosopher Karl Popper, most scientists today insist that the dividing line between science and pseudoscience is whether advocates of a hypothesis deliberately search for evidence that could falsify it and accept the hypothesis only if it survives.

Intuitive probability is driven by imaginability: the easier something is to visualize, the likelier it seems. This entraps us into what Tversky and Kahneman call the conjunction fallacy, in which a conjunction is more intuitively probable than either of its elements.

When a pilot is suspended thousands of feet in the air with nothing but empty space between him and the earth, and the horizon is obscured by clouds, haze, or mountains, his visual sense gets out of sync with reality. As he flies by the seat of his pants, which cannot distinguish acceleration from gravity, every correction makes things worse, and can send the plane into a “graveyard spiral” within minutes—the fate of an inexperienced and overconfident John F. Kennedy Jr. in 1999. As excellent as our visual systems are, rational pilots know when to discount them and turn their perception over to instruments.63 And as excellent as our cognitive systems are, in the modern world we must know when to discount them and turn our reasoning over to instruments—the tools of logic, probability, and critical thinking that extend our powers of reason beyond what nature gave us. Because in the twenty-first century, when we think by the seat of our pants, every correction can make things worse, and can send our democracy into a graveyard spiral.

Rationality is uncool. To describe someone with a slang word for the cerebral, like nerd, wonk, geek, or brainiac, is to imply they are terminally challenged in hipness.

“A man needs a little madness or else he never dares cut the rope and be free,” said Zorba the Greek.

“the ability to use knowledge to attain goals.”

When it comes to arguing against reason, as soon as you show up, you lose. Let’s say you argue that rationality is unnecessary. Is that statement rational? If you concede it isn’t, then there’s no reason for me to believe it—you just said so yourself. But if you insist I must believe it because the statement is rationally compelling, you’ve conceded that rationality is the measure by which we should accept beliefs, in which case that particular one must be false. In a similar way, if you were to claim that everything is subjective, I could ask, “Is that statement subjective?” If it is, then you are free to believe it, but I don’t have to. Or suppose you claim that everything is relative. Is that statement relative? If it is, then it may be true for you right here and now but not for anyone else or after you’ve stopped talking. This is also why the recent cliché that we’re living in a “post-truth era” cannot be true. If it were true, then it would not be true, because it would be asserting something true about the era in which we are living.

Descartes’s argument that our own existence is the one thing we cannot doubt, because the very fact of wondering whether we exist presupposes the existence of a wonderer.

Now, arguments for truth, objectivity, and reason may stick in the craw, because they seem dangerously arrogant: “Who the hell are you to claim to have the absolute truth?” But that’s not what the case for rationality is about. The psychologist David Myers has said that the essence of monotheistic belief is: (1) There is a God and (2) it’s not me (and it’s also not you).6 The secular equivalent is: (1) There is objective truth and (2) I don’t know it (and neither do you).

As the saying goes, the more we disagree, the more chance there is that at least one of us is right.

by deploying reason in other ways, we reach the moon, invent smartphones, and extinguish smallpox. The cooperativeness of the world when we apply reason to it is a strong indication that rationality really does get at objective truths. And ultimately even relativists who deny the possibility of objective truth and insist that all claims are merely the narratives of a culture lack the courage of their convictions. The cultural anthropologists or literary scholars who avow that the truths of science are merely the narratives of one culture will still have their child’s infection treated with antibiotics prescribed by a physician rather than a healing song performed by a shaman.

The philosopher Gottfried Wilhelm Leibniz (1646–1716) fantasized that logic could bring about an epistemic utopia: The only way to rectify our reasonings is to make them as tangible as those of the Mathematicians, so that we can find our error at a glance, and when there are disputes among persons, we can simply say: Let us calculate, without further ado, to see who is right.

Plane crashes, in contrast, get lavish coverage, but they kill only about 250 people a year worldwide, making planes about a thousand times safer per passenger mile than cars.17 Yet we all know people with a fear of flying but no one with a fear of driving, and a gory plane crash can scare airline passengers onto the highways for months afterward, where thousands more die.

In 2019, after a Cape Cod surfer became the first shark fatality in Massachusetts in more than eighty years, the towns equipped every beach with menacing Jaws-like warning billboards and hemorrhage-control kits, and commissioned studies on towers, drones, planes, balloons, sonar, acoustic buoys, and electromagnetic and odorant repellents. Yet every year on Cape Cod between fifteen and twenty people die in car crashes, and cheap improvements in signage, barriers, and traffic law enforcement could save many more lives at a fraction of the cost.

Nuclear power is the safest form of energy humanity has ever used. Mining accidents, hydroelectric dam failures, natural gas explosions, and oil train crashes all kill people, sometimes in large numbers, and smoke from burning coal kills them in enormous numbers, more than half a million per year. Yet nuclear power has stalled for decades in the United States and is being pushed back in Europe, often replaced by dirty and dangerous coal. In large part the opposition is driven by memories of three accidents: Three Mile Island in 1979, which killed no one; Fukushima in 2011, which killed one worker years later (the other deaths were caused by the tsunami and from a panicked evacuation); and the Soviet-bungled Chernobyl in 1986, which killed 31 in the accident and perhaps several thousand from cancer, around the same number killed by coal emissions every day.

How can we recognize the genuine dangers in the world while calibrating our understanding to reality? Consumers of news should be aware of its built-in bias and adjust their information diet to include sources that present the bigger statistical picture: less Facebook News Feed, more Our World in Data.

Journalists should put lurid events in context. A killing or plane crash or shark attack should be accompanied by the annual rate, which takes into account the denominator of the probability, not just the numerator.

A blindness to base rates also leads to public demands for the impossible. Why can’t we predict who will attempt suicide? Why don’t we have an early-warning system for school shooters? Why can’t we profile terrorists or rampage shooters and detain them preventively? The answer comes out of Bayes’s rule: a less-than-perfect test for a rare trait will mainly turn out false positives.

think about a sample of a thousand women. Out of every 1,000 women, 10 have breast cancer (that’s the prevalence, or base rate). Of these 10 women who have breast cancer, 9 will test positive (that’s the test’s sensitivity). Of the 990 women without breast cancer, about 89 will nevertheless test positive (that’s the false-positive rate). A woman tests positive. What is the chance that she actually has breast cancer? It’s not that hard: 98 of the women test positive in all, 9 of them have cancer; 9 divided by 98 is around 9 percent

how many lonely singles forgo the small chance of a lifetime of happiness with a soul mate because they think only of the large chance of a tedious coffee with a bore?

As for betting your life: Have you ever saved a minute on the road by driving over the speed limit, or indulged your impatience by checking your new texts while crossing the street? If you weighed the benefits against the chance of an accident multiplied by the price you put on your life, which way would it go? And if you don’t think this way, can you call yourself rational?

The cat that sits down on a hot stove-lid … will never sit down on a hot stove-lid again, and that is well; but also she will never sit down on a cold one any more. —MARK TWAIN

Tell people there’s an invisible man in the sky who created the universe, and the vast majority will believe you. Tell them the paint is wet, and they have to touch it to be sure. —GEORGE CARLIN

three quarters of Americans hold at least one paranormal belief. Here are some figures from the first decade of our century:7 Possession by the devil, 42 percent Extrasensory perception, 41 percent Ghosts and spirits, 32 percent Astrology, 25 percent Witches, 21 percent Communicating with the dead, 29 percent Reincarnation, 24 percent Spiritual energy in mountains, trees, and crystals, 26 percent Evil eye, curses, spells, 16 percent Consulted a fortune-teller or psychic, 15 percent

The mustering of rhetorical resources to drive an argument toward a favored conclusion is called motivated reasoning.

We evolved not as intuitive scientists but as intuitive lawyers.

In an update of a classic study showing that football fans always see more infractions by the opposing team, Kahan and collaborators showed a video of a protest in front of a building.29 When the title labeled it a protest against abortion at a health clinic, conservatives saw a peaceful demonstration, while liberals saw the protesters block the entrance and intimidate the enterers. When it was labeled a protest against the exclusion of gay people at a military recruiting center, it was the conservatives who saw pitchforks and torches and the liberals who saw Mahatma Gandhi.

As the novelist Philip K. Dick wrote, reality is that which, when you stop believing in it, doesn’t go away.

More than two billion people believe that if one doesn’t accept Jesus as one’s savior one will be damned to eternal torment in hell. Fortunately, they don’t take the next logical step and try to convert people to Christianity at swordpoint for their own good, or torture heretics who might lure others into damnation. Yet in past centuries, when Christian belief fell into the reality zone, many Crusaders, Inquisitors, conquistadors, and soldiers in the Wars of Religion did exactly that. Like the Comet Ping Pong redeemer, they treated their beliefs as literally true. For that matter, though many people profess to believe in an afterlife, they seem to be in no hurry to leave this vale of tears for eternal bliss in paradise.