Under acute stress, people typically revert to their automatic, well-learned responses. That’s evolutionarily adaptive—as long as you find yourself in the same kind of environment in which those reactions were necessary. If you’re a smokejumper, your well-learned response is to put out a fire, not start another one. If you’re fleeing for your life, your well-learned response is to run away from the fire, not toward it. In normal circumstances, those instincts might save your life. Dodge survived Mann Gulch because he swiftly overrode both of those responses.

No one had taught Dodge to build an escape fire. He hadn’t even heard of the concept; it was pure improvisation. Later, the other two survivors testified under oath that nothing resembling an escape fire was covered in their training. Many experts had spent their entire careers studying wildfires without realizing it was possible to stay alive by burning a hole through the blaze.

When I tell people about Dodge’s escape, they usually marvel at his resourcefulness under pressure. That was genius! Their astonishment quickly melts into dejection as they conclude that this kind of eureka moment is out of reach for mere mortals. I got stumped by my fourth grader’s math homework. Yet most acts of rethinking don’t require any special skill or ingenuity.

Moments earlier at Mann Gulch, the smokejumpers missed another opportunity to think again—and that one was right at their fingertips. Just before Dodge started tossing matches into the grass, he ordered his crew to drop their heavy equipment. They had spent the past eight minutes racing uphill while still carrying axes, saws, shovels, and 20-pound packs.

If you’re running for your life, it might seem obvious that your first move would be to drop anything that might slow you down. For firefighters, though, tools are essential to doing their jobs. Carrying and taking care of equipment is deeply ingrained in their training and experience. It wasn’t until Dodge gave his order that most of the smokejumpers set down their tools—and even then, one firefighter hung on to his shovel until a colleague took it out of his hands. If the crew had abandoned their tools sooner, would it have been enough to save them?

We’ll never know for certain, but Mann Gulch wasn’t an isolated incident. Between 1990 and 1995 alone, a total of twenty-three wildland firefighters perished trying to outrace fires uphill even though dropping their heavy equipment could have made the difference between life and death. In 1994, on Storm King Mountain in Colorado, high winds caused a fire to explode across a gulch. Running uphill on rocky ground with safety in view just 200 feet away, fourteen smokejumpers and wildland firefighters—four women, ten men—lost their lives.

Later, investigators calculated that without their tools and backpacks, the crew could have moved 15 to 20 percent faster. “Most would have lived had they simply dropped their gear and run for safety,” one expert wrote. Had they “dropped their packs and tools,” the U.S. Forest Service concurred, “the firefighters would have reached the top of the ridge before the fire.”

It’s reasonable to assume that at first the crew might have been running on autopilot, not even aware that they were still carrying their packs and tools. “About three hundred yards up the hill,” one of the Colorado survivors testified, “I then realized I still had my saw over my shoulder!” Even after making the wise decision to ditch the 25-pound chainsaw, he wasted valuable time: “I irrationally started looking for a place to put it down where it wouldn’t get burned. . . . I remember thinking, ‘I can’t believe I’m putting down my saw.’” One of the victims was found wearing his backpack, still clutching the handle of his chainsaw. Why would so many firefighters cling to a set of tools even though letting go might save their lives?

If you’re a firefighter, dropping your tools doesn’t just require you to unlearn habits and disregard instincts. Discarding your equipment means admitting failure and shedding part of your identity. You have to rethink your goal in your job—and your role in life. “Fires are not fought with bodies and bare hands, they are fought with tools that are often distinctive trademarks of firefighters,” organizational psychologist Karl Weick explains: “They are the firefighter’s reason for being deployed in the first place. . . . Dropping one’s tools creates an existential crisis. Without my tools, who am I?”

Wildland fires are relatively rare. Most of our lives don’t depend on split-second decisions that force us to reimagine our tools as a source of danger and a fire as a path to safety. Yet the challenge of rethinking assumptions is surprisingly common—maybe even common to all humans.

We all make the same kind of mistakes as smokejumpers and firefighters, but the consequences are less dire and therefore often go unnoticed. Our ways of thinking become habits that can weigh us down, and we don’t bother to question them until it’s too late. Expecting your squeaky brakes to keep working until they finally fail on the freeway. Believing the stock market will keep going up after analysts warn of an impending real estate bubble. Assuming your marriage is fine despite your partner’s increasing emotional distance. Feeling secure in your job even though some of your colleagues have been laid off.

This book is about the value of rethinking. It’s about adopting the kind of mental flexibility that saved Wagner Dodge’s life. It’s also about succeeding where he failed: encouraging that same agility in others.

You may not carry an ax or a shovel, but you do have some cognitive tools that you use regularly. They might be things you know, assumptions you make, or opinions you hold. Some of them aren’t just part of your job—they’re part of your sense of self.

Consider a group of students who built what has been called Harvard’s first online social network. Before they arrived at college, they had already connected more than an eighth of the entering freshman class in an “e-group.” But once they got to Cambridge, they abandoned the network and shut it down. Five years later Mark Zuckerberg started Facebook on the same campus.

From time to time, the students who created the original e-group have felt some pangs of regret. I know, because I was one of the cofounders of that group.

Let’s be clear: I never would have had the vision for what Facebook became. In hindsight, though, my friends and I clearly missed a series of chances for rethinking the potential of our platform. Our first instinct was to use the e-group to make new friends for ourselves; we didn’t consider whether it would be of interest to students at other schools or in life beyond school. Our well-learned habit was to use online tools to connect with people far away; once we lived within walking distance on the same campus, we figured we no longer needed the e-group. Although one of the cofounders was studying computer science and another early member had already founded a successful tech startup, we made the flawed assumption that an online social network was a passing hobby, not a huge part of the future of the internet. Since I didn’t know how to code, I didn’t have the tools to build something more sophisticated. Launching a company wasn’t part of my identity anyway: I saw myself as a college freshman, not a budding entrepreneur.

Since then, rethinking has become central to my sense of self. I’m a psychologist but I’m not a fan of Freud, I don’t have a couch in my office, and I don’t do therapy. As an organizational psychologist at Wharton, I’ve spent the past fifteen years researching and teaching evidence-based management. As an entrepreneur of data and ideas, I’ve been called by organizations like Google, Pixar, the NBA, and the Gates Foundation to help them reexamine how they design meaningful jobs, build creative teams, and shape collaborative cultures. My job is to think again about how we work, lead, and live—and enable others to do the same.

I can’t think of a more vital time for rethinking. As the coronavirus pandemic unfolded, many leaders around the world were slow to rethink their assumptions—first that the virus wouldn’t affect their countries, next that it would be no deadlier than the flu, and then that it could only be transmitted by people with visible symptoms. The cost in human life is still being tallied.