Common knowledge is the secret engine of social life, letting us coordinate everything from meet-ups to markets to international diplomacy. In this fascinating talk, experimental cognitive scientist Steven Pinker explores its momentous impact, threading together stories of why autocrats fear blank signs, why central bankers mumble and why saying the quiet part out loud can wreck a friendship. With wit and wisdom, he invites us to better understand the ways we get into each other’s heads — and what it means when shared norms wobble. (Recorded at TED2025 on April 8, 2025) Join us in person at a TED conference: Become a TED Member to support our mission: Subscribe to a TED newsletter: Follow TED! X: Instagram: Facebook: LinkedIn: TikTok: @tedtoks The TED Talks channel features talks, performances and original series from the world's leading thinkers and doers. Subscribe to our channel for videos on Technology, Entertainment and Design — plus science, business, global issues, the arts and more. Visit to get our entire library of TED Talks, transcripts, translations, personalized talk recommendations and more. Watch more: TED's videos may be used for non-commercial purposes under a Creative Commons License, Attribution–Non Commercial–No Derivatives (or the CC BY – NC – ND 4.0 International) and in accordance with our TED Talks Usage Policy: For more information on using TED for commercial purposes (e.g. employee learning, in a film or online course), please submit a Media Request at #TED #TEDTalks #Economics