And it is complicated by social media that can generate as well as disseminate common knowledge. Most people are mortified when their blush is followed by eye contact and becomes common knowledge. Many “spectacles of social life” – handshakes, hugs, shared meals, vacations, sex, fibs, lies, snubs, face-saving, apologies – are, at least in part, “efforts to generate or avoid the common knowledge that allows people to coordinate their actions.”Avoiding common knowledge, Pinker suggests, also shapes international relations. Pinker’s decision to “gloss over the difference between common knowledge and common belief” is disappointing, for example, especially at a time in which belief is often presented as knowledge in siloed communities embedded in a polarized society. And rationality, “that cognitive talent that underlies common knowledge,” is “what’s most special about our kind: we not only have thoughts, but thoughts about our thoughts, and thoughts about our thoughts about our thoughts.”