The main overarching argument of Think Again is that intelligence is not just about learning how to think but learning how to rethink. For Grant, a major problem is that we tend to be resistant to new ideas and alternative perspectives, digging in our heels when faced with opposing perspectives. An important marker of intelligence is cognitive flexibility, which comes from the ability to reexamine beliefs we hold in the face of new, possibly contradictory evidence. For Grant, being wrong and changing one’s mind aren’t the marks of failure as an intelligent person, but rather marks of cognitive maturity.

Grant describes this as thinking like a scientist. More specifically, he argues that when we resist rethinking, we instead act as preachers, prosecutors, or politicians, finding ways to maintain our current way(s) of thinking instead of opening ourselves up. Grant argues that we must learn how to think like scientists more often because the hallmark of thinking like a scientist is to consider new evidence and be open to changing our ideas if that evidence contradicts our current beliefs; a core line of inquiry in his project is to determine if it’s “possible to train people in other fields to think more like scientists, and if so, [if] they end up making smarter choices” (20).