A hallmark of wisdom is knowing when it’s time to abandon some of your most treasured tools—and some of the most cherished parts of your identity.

These final lines of the Prologue encapsulate one of Grant’s primary arguments: that people resist changing their minds out of fear that they will lose the mental tools and personal identities that they value. Rethinking can be seen as threatening, Grant asserts, because people conflate their identities with their opinions. By remaining open-minded, however, and moving through the fear of loss, Grant argues that people can actually gain what they fear losing, such as a clearer understanding of and deeper connection to themselves, the people close to them, and the world around them.