Summary and review ofThink Again: The Power of Knowing What You Don't Know

Reviewed by Diario de un Inversor · UpdatedJune 13, 2026

Our review

«Think Again» by Adam Grant champions a cognitive skill that institutions and organisational cultures systematically penalise: the ability to update one's beliefs when evidence changes. Grant, an organisational psychologist at Wharton, argues that in a world of accelerating change, the capacity to rethink — not merely to think — has become more valuable than intelligence or accumulated experience. The book alternates psychological research findings with concrete cases spanning crisis negotiation, political debate, and business decision-making. One of its most useful arguments for investors is the analysis of the «rethinking cycle»: how the best thinkers combine a scientist's openness with a student's humility. The honest critique is that the book is verbose — some chapters repeat the same idea through different examples — and that the investor-specific implications require the reader to draw their own conclusions. The original English edition was published in 2021.

Key takeaways

• Active rethinking — not blind perseverance — is the most valuable cognitive skill in high-uncertainty environments.
• The high-quality thinker adopts a scientist's mode: formulating hypotheses, seeking contradicting evidence, and updating conclusions without excessive emotional cost.
• The Dunning-Kruger effect and identity fusion with one's own beliefs are the primary obstacles to effective rethinking.
• In investing, the ability to recognise a thesis is wrong — and act accordingly — is more valuable than the skill of constructing the original thesis.

Fact

Adam Grant is a professor at the Wharton School (University of Pennsylvania); the book was published in English in 2021 (Viking).