One reason that might motivate a worker to accept a riskier job at higher pay, for example, would be that doing so would enable him to bid more effectively for a house in a better school district. But if other workers did likewise, none would achieve the goal they were striving for.

In short both the things we feel we need and the things available for us to buy depend largely—beyond some point, almost entirely—on the things that others choose to buy.

Getting the economy back on its feet is properly viewed as an investment in future prosperity. When businesses and consumers confront attractive investment opportunities, often the only way to seize them is by borrowing. The same is true for government. Contrary to the pronouncements of critics of economic stimulus, these investments will not impoverish our grandchildren. Continuing to allow the economy to languish in recession is the surest way to impoverish them.

Many decry rising inequality because it makes those who've fallen behind feel impoverished. But it's done much more than cause hurt feelings. It has also raised the real cost to middle-income families of achieving many basic goals. The process begins with the completely unremarkable fact that top earners have been spending at a substantially higher rate than before. They've been building bigger mansions, staging more elaborate weddings and coming-of-age parties for their kids, buying more and better of everything.

For the three decades after WWII, incomes grew at about 3 percent a year for people up and down the income ladder, but since then most income growth has occurred among the top quintile. And among that group, most of the income growth has occurred among the top 5 percent. The pattern repeats itself all the way up. Most of the growth among the top 5 percent has been among the top 1 percent, and most of the growth among that group has been among the top one-tenth of one percent.

We've long known that firms can pay higher wages if they spend less on workplace safety enhancement. Libertarians ask, "If a worker is willing to accept higher wages in return for his agreement to exercise greater caution while performing his job, why should the government prevent him from making that choice?" It's a rhetorically powerful question, yet it overlooks the fact that the agreement in question will have adverse effects on others.

The most common mistake we make as teachers is attempting to tell our students too much.