Late in his life, the 17th-century philosopher Thomas Hobbes plunged into a controversy with an Oxford professor of geometry. Hobbes believed he had discovered how to square the circle. The professor begged to differ, and Hobbes wound up looking foolish. In 1651, Hobbes had written a passage in his famous “Leviathan” that almost anticipated the episode. When power is at stake, he argued, people will dispute even something as clear as the fact that the internal angles of a triangle sum to 180 degrees. If you’ve ever seen someone — not yourself, of course — clinging doggedly to a flawed position to try to win an argument, you’ve witnessed a small instance of how what Hobbes termed a desire for “dominion” can distort reasoning.

More consequential examples are in abundant supply. On issues such as vaccines, climate change and corporate taxation, a host of individual and institutional actors now seem dogmatically chained to unreason as they pursue real or illusory power. In fact, for champions of reason, the situation is far more dire than Hobbes suspected. Even with no ulterior drive to dominion, human cognition is susceptible to a range of errors and biases that have been extensively documented over the past several decades (though in many cases these are rediscoveries of older insights).

For anyone tempted to despair, however, Steven Pinker’s new book, “Rationality: What It Is, Why It Seems Scarce, Why It Matters,” offers a pragmatic dose of measured optimism, presenting rationality as a fragile but achievable ideal in personal and civic life.

Given our current moment of apparent national derangement, when large areas of culture and politics seem to have slipped all tethers to reality, Pinker’s ambition to illuminate such a crucial topic offers the welcome prospect of a return to sanity. And in many ways he succeeds — as with all of his books, this one is erudite, lucid, funny and dense with fascinating material. His characteristic brew of Yiddish jokes, brainy comics and incisive argumentation is a pleasure to read, even when the subjects are technical and mathematical. It’s no small achievement to make formal logic, game theory, statistics and Bayesian reasoning delightful topics full of charm and relevance.

It’s also plausible to believe that a wider application of the rational tools he analyzes would improve the world in important ways. His primer on statistics and scientific uncertainty is particularly timely and should be required reading before consuming any news about the pandemic. More broadly, he argues that less media coverage of shocking but vanishingly rare events, from shark attacks to adverse vaccine reactions, would help prevent dangerous overreactions, fatalism and the diversion of finite resources away from solvable but less-dramatic issues, like malnutrition in the developing world.

It’s a reasonable critique, and Pinker is not the first to make it. But analyzing the political economy of journalism — its funding structures, ownership concentration and increasing reliance on social media shares — would have given a fuller picture of why so much coverage is so misguided and what we might do about it.

Pinker’s main focus is the sort of conscious, sequential reasoning that can track the steps in a geometric proof or an argument in formal logic. Skill in this domain maps directly onto the navigation of many real-world problems, and Pinker shows how greater mastery of the tools of rationality can improve decision-making in medical, legal, financial and many other contexts in which we must act on uncertain and shifting information. One recurring theme is the way that framing an identical choice in different ways — focusing on loss vs. gain, presenting a problem visually rather than verbally or substituting more concrete details for abstract variables — can make salient the logical core of otherwise tricky dilemmas.

Despite the undeniable power of the sort of rationality he describes, many of the deepest insights in the history of science, math, music and art strike their originators in moments of epiphany. From the 19th-century chemist Friedrich August Kekulé’s discovery of the structure of benzene to any of Mozart’s symphonies, much extraordinary human achievement is not a product of conscious, sequential reasoning. Even Plato’s Socrates — who anticipated many of Pinker’s points by nearly 2,500 years, showing the virtue of knowing what you do not know and examining all premises in arguments, not simply trusting speakers’ authority or charisma — attributed many of his most profound insights to dreams and visions. Conscious reasoning is helpful in sorting the wheat from the chaff, but it would be interesting to consider the hidden aquifers that make much of the grain grow in the first place.

The role of moral and ethical education in promoting rational behavior is also underexplored. Pinker recognizes that rationality “is not just a cognitive virtue but a moral one.” But this profoundly important point, one subtly explored by ancient Greek philosophers like Plato and Aristotle, doesn’t really get developed. This is a shame, since possessing the right sort of moral character is arguably a precondition for using rationality in beneficial ways. The capacity to be gracefully refuted in an argument is largely a moral one, and decreasing one’s desire for Hobbesian “dominion” is not something that another tutorial on statistics or game theory can achieve. For people who have mastered these formal tools and are now abusing them to gain dubious ends, something very different is needed — cultivation of the sort of moral character that allows one both to perceive and to desire the right things in life.

Rationality

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

By Steven Pinker

Viking.
412 pp. $32