Cognitive psychologist Steven Pinker’s new book, “Rationality: What It Is, Why It Seems Scarce, Why It Matters,” makes strong and optimistic claims about the value of rationality at a moment in history that seems to have turned its back on logic and rationality. And in these pages he makes perfectly clear that he’s not dealing in empty rhetoric.
Rationality – the willingness of people and societies to think clearly and act logically – has actual, pragmatic stakes in the real world. “Can poor reasoning lead to real harm, with the implication that critical thinking could protect people from their own worst cognitive instincts?” Pinker asks – and his answer is an unequivocal “Yes.”
“Rationality is a public good,” he asserts, and by the same token irrationality is a public danger. “Each of us has a motive to prefer our truth,” he writes, “but together we’re better off with the truth.”
He summons an array of those real-world issues, including social equality, climate change, educational reforms, public health, and extreme poverty, to show that progress is taking place on multiple fronts. It’s a point he fleshed out in his 2011 book, “The Better Angels of Our Nature: Why Violence Has Declined.” In that book and in his latest, he was struck by how often rationality played a key role in the steady march of progress, how many times, as he puts it, “the first domino was a reasoned argument.”
At the heart of Pinker’s book is the concept of Bayes’ theorem, an application of rationality first devised by Thomas Bayes in the 18th century. Bayes’ rule is, at heart, a strict method of estimating the probability of truth, either in a hypothesis or in evidence. It asks: How probable is a given hypothesis, in light of the available data? And does the available data call for a different hypothesis? Bayes’ rule deals in likelihoods, and although Pinker indulges in a good deal of technical explanation, he also stresses that Bayesian thinking can also operate on a surprisingly gut level – it’s not an Ivory Tower abstraction.
And, as Pinker emphasizes throughout, a Bayesian approach is badly needed in the present moment. His book appears at a time when people are not only increasingly living in carefully curated private bubbles, but some of them are also believing conspiracy theories and false reports of elections being stolen – and a small number are willing to defend their irrationality with violence.
If Pinker’s “Rationality” has one weakness, it’s the book’s readiness to dismiss the obvious force-multiplier behind the enormous rise in irrationality: social media. He writes that blaming social media for all, or even most, of this unreasonableness would be “too glib to be satisfying” – itself, ironically, an overly glib answer. “We must go beyond offhand excuses that just attribute one irrationality to another,” Pinker writes. He disparages the tactic of explaining that people embrace false beliefs simply because those beliefs make them feel better, pointing out that this “only raises the question of why people should get comfort and closure from beliefs that could not possibly do them any good.”
In a book so elegantly written and so generously packed with data and references, this is the only jarringly blithe (and jarringly non-Bayesian) note. (One could point out that the only irrational entity here is the end-user; the social media companies are intentionally monetizing users’ irrationality, which is built into their platforms’ business models.) Social media’s effects on collective rationality are so great and so obvious that it’s a shame a book called “Rationality” doesn’t deal with the whole element more seriously.
The concept of collective rationality is important to the dogged optimism that runs throughout Pinker’s book. He contends that humans think together better than they think separately, and the implication is clear: If we improve the teaching of rationality and critical thinking, we will continue to improve society. “Rationality” will improve your own critical thinking – pass it on.