Greensburg — Twenty years ago, a business consultant wrote a book that led to a training video that influenced students across the country.

In celebration, this column will take a look back at Joel Arthur Barker’s breakthrough on the subject of paradigms, published by HarperCollins.

First, what is a paradigm? Barker borrowed the term from Thomas Kuhn, where it was adopted to refer to a mental model that someone uses to perceive the world. A paradigm is a belief that is so familiar that we take it for granted and assume it is true. We see the world through paradigms, in the same way that some of us see the world through eyeglasses.

Paradigms indicate to us what is going on. Paradigms tell us how to act. In a courtroom, you stand up when the judge enters. In the Gettysburg cemetery, you are quiet. When you are in line, don’t jump ahead of the next guy. Simple things like that. Teachers use paradigms for the classroom. Coaches use paradigms for their sport. Bosses operate using them as well.

What interested Barker was the possibility of paradigm shifts. A paradigm shifts when you replace a dominant paradigm with a new one. New game, new rules. So maybe you used to believe that a high school diploma prepared you for satisfactory jobs, but now you have decided instead that a college degree is the way to go. That is a paradigm shift over the last fifteen years.

Barker wanted leaders especially to become aware of their own paradigms, in case they need to shift. He wrote about the Swiss watchmakers who overlooked the digital revolution and lost market share for their fine pieces when Japan started producing electronic versions at lower cost. The Swiss failed to make the paradigm shift.

At some point, your little girl became a woman. Uh-oh. Paradigm shift. The reality has changed. You have to see that change for what it is. Sometimes, though, reality didn’t change. Instead, your perceptions of the same reality changed. At one point, people believed the earth was flat. Eventually, they came to understand that it is spherical. Paradigm-shift.

Even the best paradigms leave certain problems unanswered. A paradigm cannot account for every detail. A paradigm is an approximation, the best we can do. But like I said, reality changes. And even when it doesn’t change, there are little things the paradigm couldn’t include. Sometimes, the little things are the important things.

A columnist like me repeatedly offers new paradigms, alternative ways of seeing the world around you. They point to details you might have overlooked. Or they suggest contrary methods for making sense of everyday events. Notice how the pundits are trying to explain why Romney lost. They use competing “paradigms” to convince us.

Barker explained that within a paradigm, a leader simply manages things, helping folks reach their goals. The real proof of a leader is in the spaces between paradigms, challenging how we think and urging us to envision new possibilities. When the people aren’t sure what to think, they require a leader with vision. And another word for that vision is “paradigm.”

Local governments have been struggling to find the language to describe their newfound status. They are stuck with old language. They are stuck with old habits. They are stuck with old laws. But those old paradigms are inadequate to a complex reality, and many politicians know it. They feel it. The trick in part is trying to convince the rest of us, who want desperately to believe that nothing in our hometown ever changes. It is changing, profoundly. Just ask your kids.

Joel Barker’s book is a little outdated today. For example, he warned us against the coming dominance of Japan’s industrial sector. So, okay, he missed that one. Still, his book is more about the process of paradigms than about any particular guess he might have made about the future. In that respect, at least, it endures.