Rationality: What It Is, Why It Seems Scarce, Why It Matters, by Steven Pinker (New York, NY: Random House/Penguin/Viking, 2021, ISBN 9780525561996). 432 pp. Hardcover, $32.00.
Steven Pinker is one of my intellectual heroes. I have read and benefitted from his previous work on language (The Language Instinct, Words and Rules), cognition (How the Mind Works, The Blank Slate), and human progress (The Better Angels of Our Nature, Enlightenment Now). I share his disdain for the postmodern relativism that has debased so much of academia, and I agree with his attribution of humanity’s progress over the past five hundred years to humanism, understood as the reason- and evidence-based worldview that came into prominence with the Enlightenment.
So I looked forward to reading and reviewing Pinker’s latest book, Rationality: What It Is, Why It Seems Scarce, Why It Matters. The book begins with two chapters that demonstrate the ubiquity of human irrationality and make a preliminary case for the value of rational thought. Its concluding two chapters address the last two subtitles, explaining why rationality is scarce and why it’s needed for our individual and collective flourishing. Most of the book, Chapters 3 through 9, “explain the most widely applicable normative tools of reason” (7), techniques Pinker regards as the keys to rational thought.
This seems promising, does it not? Alas, while Rationality is engaging and well-written—replete with the memorable examples, humor, and clever comments so characteristic of Pinker’s prose—ultimately, the book was, for this reader at least, disappointing.
* * *
Rationality is generally thought to comprise the use of reason, being reasonable, and having good reasons for one’s beliefs and actions. This focus is reflected in teaching and research on critical thinking, which includes logic (deductive reasoning), practical (non-deductive) reasoning, reasoning mistakes (fallacies), and argumentation. To recognize the strengths and limitations of Pinker’s book, it’s helpful to understand these concepts in greater depth.
Books and courses on logic typically focus entirely on deduction/deductive reasoning. Like mathematics, deduction is purely formal, deriving conclusions from structure rather than content. Thus, 2 + 2 = 4 whether one is dealing with apples or automobiles. Similarly with deduction: If x is true, and x implies y, then y must be true for all x’s and y’s that satisfy the two premises. For instance, let x be “It’s snowing outside” and let y be “If it’s snowing outside, the atmospheric temperature must be 32 degrees F or colder.” Then, from observations that it’s snowing outside, one can conclude that the atmospheric temperature is 32 degrees F or colder, and this conclusion is guaranteed to be true because it follows validly from true premises. The critical component of deductive reasoning is the “x implies y” premise, also expressed as “If x, then y.” Known as “logical implication,” this premise must be absolutely true without exceptions. Unfortunately, in practical affairs, such relationships are rarely found. Yes, if we know that Lassie is a collie, and that “If collie, then dog,” we can reliably infer that Lassie is a dog. So what? This deduction didn’t help us find out something we didn’t already know. Because there aren’t many interesting, exception-less “x implies y” real-world relationships, there aren’t many practical situations for which deduction will get us to usefully informative conclusions.
If deduction was the entirety of human reasoning, reasoning itself would be mostly a waste of time. Fortunately, there’s a large, poorly defined, realm of non-deductive reasoning. Sometimes called “practical reasoning” because of its relevance to practical affairs, this is the kind of thinking we do when trying to solve problems—“Why won’t my car start?”—understand things, and generally make our way in the world. Because it uses exception-riddled, everyday premises, practical reasoning yields conclusions that are fallible and potentially mistaken. Consider the following argument: “President Biden’s approval rating is quite low. So he’s not likely to be reelected.” This argument can be represented as reasoning involving the implication “If a president’s approval rating is quite low, that president is not likely to be reelected.” Because this premise states a likelihood, not a certainty, the argument’s conclusion must also be a likelihood. In fact, presidents with low approval ratings after their first year in office—such as Ronald Reagan in 1981—have been reelected. Yet even though the conclusions of practical reasoning are uncertain, this kind of reasoning is much more relevant to and useful in our everyday affairs.
Rationality’s third chapter addresses reasoning. It includes a valuable primer on deductive reasoning as well as a poorly developed review of important fallacies—mistakes of deductive and non-deductive reasoning. However, this chapter says little about practical reasoning or argumentation, the ways we use reasons as well as emotional and various non-rational appeals to persuade others. Thus, with the exception of deduction, reasoning receives little attention and is not central to Pinker’s notion of rationality.
What is central is an alternative view of rationality developed in the social and behavioral sciences, especially economics and some parts of psychology. I learned this “rational person” account of human behavior while earning a PhD in decision sciences. It attributes rationality to people who choose courses of action that are most likely to maximize their utility or preference satisfaction. Because one rarely knows what outcomes will result from decision alternatives, decision makers must rely on probabilities, quantitative expressions of likelihood that are sometimes based on statistical data. Various formal methods have been developed to assist decision makers in such situations—Bayesian statistics, expected utility theory, statistical decision theory, and game theory, among others. These are the “tools of rationality” that occupy most of Pinker’s book. In a way this isn’t surprising given that Rationality is based on a course Pinker teaches to Harvard undergraduates: Intelligent students, and many academic colleagues, are impressed by the rigor of formal, mathematical methods.
It isn’t that these formal decision methods are wrong but rather, like deductive reasoning, they rarely apply in real-world situations. For instance, few major corporate decisions—involving, say, the introduction of innovative new products or acquisitions of other companies—are made with these tools. They are used even less frequently in our personal lives. Why? Because real-world decisions call for case-specific information, not the generalized “base rates” used in Bayesian statistics and other such methods. A would-be entrepreneur might know that less than 20 percent of new business ventures succeed, but she would never accept that base rate as the likelihood that her proposed venture will make money. Statistical information can be useful in medical decision making—“This operation has a 93 percent probability of being successful”—but that is typically not the case in the unique, highly individuated, situations faced by organizations and individuals in their personal lives.
The other “reasons-based” rationality that Pinker largely overlooks is taught in critical thinking courses and is addressed by academic research on practical reasoning and argumentation. The work of Douglas Walton is exemplary. Unlike deduction, practical reasoning is fallible and highly varied, encompassing induction (reasoning from specific instances to a general conclusion), abduction (inference to the best explanation), similarity-based reasoning, and causal reasoning, among others. Because Rationality doesn’t address these kinds of reasoning, it fails to point out the mistakes to which they are vulnerable. Thus, because inductive reasoning relies on large representative samples of a population, it is vulnerable to the fallacy of “hasty generalization,” our tendency to reach broad general conclusions—“Republicans are racists”—based on small or nonrepresentative samples. Reasoning based on similarity necessitates that one focus on key similarities while recognizing important differences between the things being compared. Ignoring such differences exposes one to the fallacy of “false analogy.” Former President Reagan once asserted that federal government spending could be reduced by cutting taxes, because the government was like a child whose spending would go down if his allowance was reduced. Reagan’s analogy failed to note that, unlike children, the federal government can borrow or print virtually unlimited amounts of money. None of Pinker’s “tools of rationality” would help one critique Reagan’s argument.
The book’s chapter on causal reasoning, an important type of practical reasoning, demonstrates its shortcomings. Titled “Correlation and Causation,” the chapter rightfully addresses the serious mistake of inferring a causal relationship between two variables that are statistically correlated. It goes on to discuss the challenges researchers face in generating and interpreting empirical data that might allow them to identify the causal relationships with which science is so centrally concerned. The chapter includes a brief discussion of causation itself, within which can be found complications such as the distinction between causes and conditions: a condition is an enablement (oxygen and flammable material) that is necessary but less active than the cause (a source of spark) responsible for an outcome (one’s house burning down). But lacking development, Pinker’s discussion would not enable readers to recognize the poor reasoning in a common bumper-sticker argument against gun control: “Guns don’t kill people; people do.” Yes, people are the cause of these deaths because guns are a condition or enablement. Sometimes, to prevent an outcome, it may be easier to control a condition (the availability of guns) than to control the cause (the angry and irrational behavior of people).
Rationality correctly identifies confirmation or my-side bias as a pervasive cause of poor reasoning: We look for evidence that is consistent with our initial beliefs and ignore or misinterpret data that could challenge those beliefs. An equally harmful failing receives scant attention: We habitually “jump to conclusions,” inferring too strongly based on limited information. Surprisingly given his knowledge of linguistics, Pinker barely mentions the role of language in thought and the ways language can mislead. Thus, there is no discussion of conceptual vagueness, the lack of clear boundaries for many important concepts, and the way this gives rise to “conceptual stretching,” applying a concept far beyond its normal meaning. In today’s partisan political environment, most people accused of being “socialists,” “racists,” or “fascists” are victims of conceptual stretching.
The most valuable parts of Rationality are its concluding two chapters. Chapter 10, “What’s Wrong with People,” explains why irrationality is so prevalent. It cites two of the “usual suspects”—motivated reasoning and myside bias—while making a strong case for another, less widely recognized, cause: Many people “divide their worlds into two zones” (299), an everyday world of physical objects in which one’s beliefs are intended to represent reality and a “world beyond immediate experience” (300) in which beliefs are untethered from reason and reality because they satisfy nonrational spiritual or mythological needs. This is why people cannot be argued out of religious beliefs that aren’t accountable to reason or evidence in the first place. Explaining “Why Rationality Matters” in Chapter 11, Pinker highlights influential historical arguments against religious persecution, cruel punishment, slavery, and the oppression of women. Ironically, while some of these arguments employ an informal version of cost-benefit analysis, none use the formal “tools of rationality” Pinker promotes in his book. They instead rely on the non-deductive practical reasoning we do in everyday affairs. For instance, he cites Jeremy Bentham’s argument against cruelty to animals, an instance of similarity-based reasoning: If we protect human beings from suffering, even those who cannot reason or talk, should we not do the same for animals that are also able to suffer?
Summing up, while Pinker has done humankind a service by promoting rationality, he mostly misses the mark in explicating what it involves.