Deep thoughts

Devoted readers of the estimable Montreal-born psychologist Steven Pinker know he can get carried away with his own brilliance.

In his 12 previous pop-science books — among them such bestsellers as The Language Instinct, How the Mind Works and Enlightenment Now — he has been known to test the patience of his followers with both the complexity and wordiness of his arguments.

His new effort, an often brain-busting disquisition on how so-called common knowledge greases the wheels of human interaction, is no exception.

Here is an unfortunate sentence from page 72 of When Everyone Knows That Everyone Knows… in which he is talking about the logical problems with holding firm beliefs:

“Since a Bayesian posterior is just a prior multiplied by the likelihood of the evidence divided by the commonness of the evidence, if the likelihood of the evidence against your pet belief is embarrassingly high, just say that your priors are low, and you can jigger the posterior to be as low as you like!”

Got that in less than three re-readings? If so you too, like Pinker, could hold a job as a Harvard professor and one of the West’s leading public intellectuals, up there with the likes of Malcolm Gladwell, Jonathan Haidt and Neil DeGrasse Tyson.

Granted, the sentence quoted above cherry picks unfairly. But the truth remains that much of the first two-thirds of When Everyone Knows gets so bogged down in logic puzzles and academic proofs that even the most generous-minded reader will have trouble staying tuned in.

To cut to the chase, Pinker’s point is that there is a huge difference between how we act when we assume our information is proprietary and when he know it is widely available — or, rather, “common knowledge.”

It affects whether we blush or whether we laugh. It affects whether we offer truthful opinions or tell white lies. It can make the difference between people wanting to live in peace or going to war.

In his early pages, Pinker introduces the key notion of “recursive mentalizing.” He defines this as the human mind’s propensity toward “thinking about other people’s thoughts about still other people’s thoughts.”

He devotes a good hunk of the book to exploring and explaining the implications of this complicated idea. He draws from the research of a variety of prominent academics, including the mathematician Robert Aumann, anthropologist Alan Fiske and the sociologist Erving Goffman.

Pinker doesn’t just play to the highbrow crowd. He makes an effort to leaven his seriousness wherever possible to relate to the average reader with jokes and quotations from all sorts of pop-culture sources.

But it’s really not until the final third of the book where Pinker gets to where he is going, and you begin to see why thinking about what other people think matters so much in human affairs.

He has an excellent section on the public nature of humour, and a fascinating one on the importance of euphemisms.

Perhaps the most timely chapter is on our “cancelling instinct,” the impulse to silence those whose views oppose our own.

A liberal in the classic sense, he takes issue with his American university’s recent attempts to enforce politically correct ideas around everything from gender ideology to the war in Gaza.

“Even when the academic consensus is almost certainly correct, as with vaccines and climate change, skeptics can understandably ask, ‘Why should we trust the consensus, if it comes out of a clique that brooks no dissent?’”

At 71, Pinker shows no signs of wanting to relinquish his podium. He recently released a Ted talk on the subject of this new book. It provides a good place to gauge one’s interest in what can be a challenging read.

Morley Walker is a retired Free Press editor and writer.