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

by Steven Pinker

Rationality ought to be the lodestar for everything we think and do. (If you disagree, are your objections rational?) Yet in an era blessed with unprecedented resources for reasoning, the public sphere is infested with fake news, quack cures, conspiracy theories, and “post-truth” rhetoric.

Yet among our fiercest problems today is convincing people to accept the solutions when we do find them.

am among the first to insist that 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.

As we shall see, when people are given problems that are closer to their lived reality and framed in the ways in which they naturally encounter the world, they are not as witless as they appear.

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. These tools of reasoning are indispensable in avoiding folly in our personal lives and public policies.

Many act as if rationality is obsolete—as if the point of argumentation is to discredit one’s adversaries rather than collectively reason our way to the most defensible beliefs.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

realism and reason are ideals that must be singled out and defended.

Man is a rational animal. So at least we have been told. Throughout a long life I have searched diligently for evidence in favor of this statement. So far, I have not had the good fortune to come across it. —Bertrand Russell

We have postponed our expected date with death from thirty years of age to more than seventy (eighty in developed countries), reduced extreme poverty from ninety percent of humanity to less than nine, slashed the rates of death from war twentyfold and from famine a hundredfold.

Even when the ancient bane of pestilence rose up anew in the twenty-first century, we identified the cause within days, sequenced its genome within weeks, and administered vaccines within a year, keeping its death toll to a fraction of those of historic pandemics.

The San also engage in critical thinking. They know not to trust their first impressions, and appreciate the dangers of seeing what they want to see.

Another critical faculty exercised by the San is distinguishing causation from correlation.

People gamble and play the lottery, where they are guaranteed to lose, and fail to invest for their retirement, where they are guaranteed to win.

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

the ability to outsmart nature with language, sociality, and know-how.14 If contemporary humans seem irrational, don’t blame the hunter-gatherers.

To understand what rationality is, why it seems scarce, and why it matters, we must begin with the ground truths of rationality itself: the ways an intelligent agent ought to reason, given its goals and the world in which it lives. These “normative” models come from logic, philosophy, mathematics, and artificial intelligence, and they are our best understanding of the “correct” solution to a problem and how to find it.

Sometimes the disparity reveals a genuine irrationality: the human brain cannot cope with the complexity of a problem, or it is saddled with a bug that cussedly drives it to the wrong answer time and again. But in many cases there is a method to people’s madness.

The penultimate chapter will lay out how some of today’s florid outbursts of irrationality may be understood as the rational pursuit of goals other than an objective understanding of the world.

Though explanations of irrationality may absolve people of the charge of outright stupidity, to understand is not to forgive. Sometimes we can hold people to a higher standard.

Since a recurring insight of the study of judgment and decision making is that humans become more rational when the information they’re dealing with is more vivid and relevant, let me turn to examples.

two cognitive systems, later made famous by Kahneman (his sometime coauthor) in the 2011 bestseller Thinking, Fast and Slow. System 1 operates rapidly and effortlessly, and it seduces us with the wrong answers; System 2 requires concentration, motivation, and the application of learned rules, and it allows us to grasp the right ones.

System 1 means snap judgments; System 2 means thinking twice. The lesson of the Cognitive Reflection Test is that blunders of reasoning may come from thoughtlessness rather than ineptitude.

Time and again people turn over the P, or the P and the Q, and fail to turn over the not-Q.24 It’s not that they’re incapable of understanding the right answer. As with the Cognitive Reflection Test, as soon as it is explained to them they slap themselves on the forehead and accept it.25 But their unreflective intuition, left to its own devices, fails to do the logic.

confirmation bias: the bad habit of seeking evidence that ratifies a belief and being incurious about evidence that might falsify it.26 People think that dreams are omens because they recall the time when they dreamt a relative had a mishap and she did, but they forget about all the times when a relative was fine after they dreamt she had a mishap.

Confirmation bias is a common diagnosis for human folly and a target for enhancing rationality. Francis Bacon (1561–1626), often credited with developing the scientific method, wrote of a man who was taken to a church and shown a painting of sailors who had escaped a shipwreck thanks to their holy vows. “Aye,” he remarked, “but where are they painted that were drowned after their vows?”

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.

Cognitive psychologists debate exactly what kinds of content temporarily turn people into logicians.

Monitoring a privilege or duty is one of these logic-unlocking themes; monitoring danger is another.

Logic, by definition, is about the form of statements, not their content:

illusions such as the gambler’s fallacy, in which people misguidedly think that after a run of reds the next spin of the roulette wheel will turn up black, when in fact the wheel has no memory, so every spin is independent.

New information reduces our ignorance and changes the probability.

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.

Kahneman has observed that humans are never so irrational as when protecting their pet ideas.

In an “adversarial collaboration,” the disputants agree in advance on an empirical test that would settle the matter, and invite an arbiter to join them in carrying it out.

This is a hard problem because the information coming into the brain from the retina doesn’t reflect reality directly.

A shape on the retina depends not just on the 3-D geometry of the object but on its orientation from a vantage point:

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.

May I say that I have not thoroughly enjoyed serving with humans? I find their illogic and foolish emotions a constant irritant. —Mr. Spock

To begin at the beginning: what is rationality?

A definition that is more or less faithful to the way the word is used is “the ability to use knowledge to attain goals.” Knowledge in turn is standardly defined as “justified true belief.”

A rational agent must have a goal, whether it is to ascertain the truth of a noteworthy idea, called theoretical reason, or to bring about a noteworthy outcome in the world, called practical reason (“what is true” and “what to do”).

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.

The very fact of interrogating the concept of reason using reason presupposes the validity of reason.

We can expose the rules of reason and distill and purify them into normative models of logic and probability.

Another reassurance that reason is valid is that it works. Life is not a dream, in which we pop up in disconnected locations and bewildering things happen without rhyme or reason.

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.

Would particular measures merely be feel-good signaling that leaves the oppressed groups no better off? Would they make matters worse? Advocates of social justice need to know the answers to these questions, and reason is the only way we can know anything about anything.

In introducing the case for reason, I wrote, “As long as people are arguing and persuading . . . ,” but that’s a big “as long as.” Rationality rejecters can refuse to play the game. They can say, “I don’t have to justify my beliefs to you. Your demands for arguments and evidence show that you are part of the problem.” Instead of feeling any need to persuade, people who are certain they are correct can impose their beliefs by force.

Modern universities—oddly enough, given that their mission is to evaluate ideas—have been at the forefront of finding ways to suppress opinions, including disinviting and drowning out speakers,