When Everyone Knows That Everyone Knows

Book review by Dr Anne Sarzin

The title of Professor Steven Pinker’s latest book hints at its major theme of recursive meanings, When everyone knows that everyone knows: Common Knowledge and the Science of Harmony, Hypocrisy and Outrage.

The kernel of that title is to be found in its first phrase, ‘When everyone knows that everyone knows,’ a statement Pinker then expands ad infinitum, ‘When everyone knows that everyone knows that everyone knows that everyone knows,’ and that’s just the beginning of his labyrinthine text that will attract readers who love enigmatic brain teasers and, equally, it will repel others whose heads are too small to hold the infinitude of phrases and meanings embedded repetitively in his text. The strengths of this book, therefore, are also its weaknesses—while the intellectual complexity of his arguments, undoubtedly, will enthral many readers, those same arguments will discourage many others. This book insistently demands the reader’s unremitting focus and concentration in order to probe and decode its dense arguments and hypotheses.

That said, there are rewards for the reader’s persistence in listening to Pinker, generally acknowledged as one of the world’s celebrated intellectuals, who has spent a lifetime thinking about how we think and demonstrating to his readers that this awareness of common knowledge makes us human. Currently the Johnstone Family Professor of Psychology at Harvard University, Pinker has a loyal following of devotees and continues to wield enormous influence in academia and in the real world, presenting his own experimental work and hypotheses in popular books aimed at the general reader. His assertion that the power of cognition to take its own outputs and feed them back into more cognition is a theme that runs through all his books.

In his latest book, Pinker propels one into a dizzying vortex of swirling thoughts that, at times, negatively impact his intention to communicate his work as simply as possible. While he might strive to express himself with simplicity, it is a deceptive strategy, as it cloaks the challenging depth of thinking demanded of his readers. He contends these trains of thought are, ‘exercises of recursive mentalizing, the cognitive talent that underlies common knowledge’. Pinker states that he aims to explain the ‘obscure but momentous’ research on common knowledge and how the concept illuminates many enigmas of our public affairs and personal lives. He shows how common knowledge explains fundamental features of societal organisation, such as political power and financial markets, as well as aspects of human nature, ‘such as laughter and tears and countless curiosities of private and public life, such as bubbles and crashes, road rage, anonymous donations, long goodbyes, revolutions that come out of nowhere, social media shaming mobs and academic cancel culture’.

The chapter headings are perhaps among the most intriguing aspects of this book, ranging from ‘The Emperor, the Elephant, and the Matzo Ball’ and ‘Reading the Mind of a Mind Reader’, to ‘Laughing, Crying, Blushing, Staring, Glaring’ and ‘Radical Honesty, Radical Hypocrisy’. They sound eminently accessible, but don’t be fooled by these alluring signposts to Pinker’s ideological maze. Despite the jokes sprinkled liberally throughout the text as literary leavening, mastering these arguments is never easy other than, one would imagine, for those possessing the skillsets of psycholinguists, psychologists, cognitive scientists and those in related disciplines.

If this book sounds like an uphill battle, it’s worth it for the view that opens up and richly rewards the reader. In particular, the chapter ‘The Department of Social Relations’ offers an analysis and insightful exposition of philanthropy, drawing inspiration from Moses Maimonides’ ‘Ladder of Charity’.  According to Maimonides, the righteousness of a charitable gift cannot be reckoned by the size of the donation alone but depends on the circumstances of giving, and the state of knowledge of the donor and the beneficiary. Maimonides’ distinction between private and common knowledge was the impetus for research Pinker and his team conducted to determine why levels of mutual knowledge should have such a potent effect on ‘attributions of charitability’. Pinker states, ‘We wanted to see whether the intuitions held up eight hundred years later’. He concludes that Maimonides was ‘mostly’ right—states of mutual knowledge do affect judgements of charitability.

Especially fascinating is Pinker’s discussion of the public insult that sparks a lethal brawl and communal outrage. He recalls poignantly his grandmother’s earliest memory of the rumours that sparked the Kishinev pogroms—rumours that Jews had murdered a Christian boy to make matzo with his blood. He contends that the annals of history are filled with examples and that this dynamic has continued to shape history in this century. Pinker doesn’t resile from analysis of controversial areas of contemporary life, for example, he tackles the role of common knowledge in academic cancel culture, stating, ‘in defiance of their universities’ mission statements, many academics believe that the primary purpose of a university is not to discover and transmit knowledge but to pursue social justice, conceived as the wresting of power by victim groups from oppressor groups’. He views young scholars with strong urges to censor as an ominous sign for the future of the academy. He reports that a majority of surveyed academics under 35 years of age say they are in favour of shutting down speakers with whom they disagree on a particular issue; and a fifth support students who would use violence to prevent a speaker from airing views they consider offensive (Honeycutt, Stevens, & Kaufmann, 2021). ‘The recent metaphor for this repression, deplatforming, is telling: being on a platform, visible to all, is what allows a speaker to generate common knowledge,’ he writes. ‘What terrifies the censors and cancelers, it appears, is not that a dangerous idea might be thought, or even expressed, but that it might become common knowledge….But once something is not just known but known to be known, it can rewrite the rules.’

Pinker demonstrates his intellectual grasp of contentious issues in contemporary life conclusively.  In these areas, he proves enlightening, enabling us to discern and identify falsifications that are common in academia and in the marketplace of civil discourse.

Pinker’s deep dive into common knowledge provokes the reader to follow where he leads. Finally, readers arrive at a place where ‘we not only have thoughts, but have thoughts about our thoughts, and thoughts about our thoughts about our thoughts’. Pinker’s triumph is persuading his readers to journey with him to this point of understanding and enlightenment.

When everyone knows that everyone knows: Common knowledge and the Science of Harmony, Hypocrisy and Outrage

Steven Pinker

Allen Lane, an imprint of Penguin Random House UK

2025