The stock market has been booming for a while now. However, other measures of economic growth haven't done so well--in some instances for decades. One theory for that anemic economic growth is what former Treasury Secretary and Harvard University President Larry Summers and other economists call "secular stagnation," or basically, the notion that all the big ideas have already been thought of.

The exhaustion of big ideas as the reason for a stagnating economy is also the premise of Northwestern University economist Robert Gordon's book The Rise and Fall of American Growth: The U.S. Standard of Living Since the Civil War.

Gordon and Summers aren't the first economists to think poor economic performance means all the good ideas are gone. Alvin Hansen was one of the most important and influential economists who ever lived. He played an important role in creating the White House Council of Economic Advisors, as well as the Social Security system.

Alvin Hansen also believed the economy was stagnating because every innovation that could move the economy forward already existed.

Hansen shared his theory of secular stagnation in the late 1930s, before modern jet travel, nuclear power, computers (both personal and the so-big-it-takes-up-a-whole-room kind), cellular technology, and a whole bunch of other innovations were really a thing. Hansen also shared his theory prior to a series of societal innovations that gave minorities and other underrepresented groups a greater chance to participate in changing the economy.

In other words, one of the smartest economists of all time believed he had seen all the good ideas in an era when Augusta Uwamanzu-Nna would have been a science fiction character rather than a living, breathing person.

The point of that last sentence isn't that we've fixed every problem from the 1930s.

The point is that there are always problems to be fixed, and there are always new ideas about how to fix those problems. And, though it feels like we haven't made enough progress when it comes to inclusion, every decade there is greater diversity in the type of people involved in solving society's problems through innovation.

Eighty years from now, my great-grandchildren will look back at a belief that every idea that could move the economy forward already existed in 2017 and laugh. But, given human nature, there is also a good chance that they will also believe that in their time, as this century ends, all the good inventions will have already been invented.

Human beings tend to do that. We like to believe that history ends with us.

But Alvin Hansen was wrong when he thought that.

The economists of our generation are wrong to think that.

The thinkers and leaders who believe that in 2100 will be wrong, too.

Growth is not a given, nor does it have some sort of inherent limitation. It is the result of choices we collectively make. If we've really stopped growing, it isn't because we don't have any more good ideas.

It's because we've shifted our priorities away from the things that fuel growth: Education and innovation.

And we need to change that, if we want to grow again.