Adam Smith's uncritically enthusiastic modern disciples portray his invisible hand theory as saying that market forces reliably harness selfish individuals to serve the common good. That's often true, but as Darwin recognized clearly, many traits that serve the interests of individual animals make life more difficult for larger groups.

The fact that many private expenditures are mutually offsetting actually happens to constitute a remarkably good bit of fiscal news. Mutually offsetting spending patterns are wasteful in the same way that military arms races are. In such situations, if each party spends less, nothing is sacrificed, yet resources are freed up that can be put to much better uses.

As John Maynard Keynes taught us in the 1930s, in such situations, government is the only entity with both the motive and the ability to boost total spending by enough to put people back to work. As it happens there are long lists of important public projects that cry out to be done.

Rising inequality hasn't really accomplished anything of value for its ostensible beneficiaries, the top one percent. They've all built bigger mansions and staged more lavish parties. But in so doing, they've simply raised the bar that defines what's considered adequate in these categories.

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.

We could curtail private spending by several trillion dollars a year without requiring painful sacrifices from anyone. That would be more than enough to rebuild our crumbling infrastructure and eliminate government indebtedness once and for all.