My Thanksgiving column about how the pilgrims nearly starved practicing communal farming but thrived once they switched to private cultivation made some people angry. One commented, "Sharing of the fruits of our labor is a bad thing?"

I never said that.

I practice charity regularly. I believe in sharing. But when government takes our money by force and gives it to others, that's not sharing.

And sharing can't be a basis for production -- you can't share what hasn't been produced. My point is that production and prosperity require property rights. Property rights associate effort with benefits. Where benefits are unrelated to effort, people do the least amount necessary to get by while taking the most they can get. Economists have a pithy way of summing up this truth: No one washes a rental car.

It's called the "tragedy of the commons." The idea is as old as ancient Greece, but ecologist Garrett Hardin popularized the phrase in a 1968 Science magazine article. Hardin described a common pasture on which anyone may graze his livestock. Each person will benefit from a larger herd but will suffer only a tiny fraction of the negative effects of overgrazing. Public Choice economists call this "concentrated benefits and dispersed costs."

That's a recipe for depleting the resource. If a herdsman were to leave a portion of the commons ungrazed, someone else would gain the benefit, so why leave it ungrazed? Soon, all the grass is gone, and the livestock die. That's the tragedy of the commons.

There are two possible solutions. One is to put someone in charge. But that someone would have arbitrary power over the rest -- he may give his friends better terms -- and one individual can't possibly know how to plan the village economy.

The second solution, as the pilgrims learned the hard way, is private property. Property rights unite costs and benefits. If a herdsman owns part of the pasture, he reaps not only 100 percent of the benefits of enlarging his herd but also 100 percent of the costs. Under those conditions, he behaves differently. If he undergrazes, uses fewer pesticides, etc., to make sure that the pasture flourishes next year, he can anticipate the future benefits. So, he has a strong incentive to be a good steward of the land.

This principle is pertinent today. People lament endangered species and call for government action. But that is the inferior "solution" already discussed. What we need is private property.

Cows, chickens, turkeys and pigs are never at risk of becoming endangered. What's special about them? Only that individuals own these animals and sell them. That gives livestock owners an incentive to keep them healthy and plentiful year after year.

The animals whose future we do worry about -- whales and elephants, for example -- are not typically subject to ownership. It's the tragedy of the commons.

Elephants are endangered because in much of Africa, poachers kill them for their tusks. Poachers have no incentive to expand herds, and neither does anyone else. Governments outlawed hunting and the ivory trade, but that hasn't stopped the loss of elephants. The plain is too vast to police it all.

Yet, where the property principle has been applied -- however imperfectly -- the fate of the elephants has been reversed. Villagers in Zimbabwe earn income by permitting hunting. In effect, the villagers have property rights in the herds. That changes attitudes. They'd be poorer if they let the elephants be hunted to extinction.

The result? "To say that we have too many elephants would be an understatement," Zimbabwe Department of National Parks and Wildlife Management acting director E.W. Kanhanga said in 2001.

The system is not perfect because individual property rights -- which would create a stronger sense of responsibility -- are not allowed. Moreover, the system has come under suspicion because cronies of Zimbabwe's despicable dictator, Robert Mugabe, are said to be killing elephants in game parks.

Nevertheless, Zimbabwe tried property rights. Kenya tried prohibition. Kenya lost elephants while Zimbabwe gained them. [http://tinyurl.com/22xdrp].

The pattern is clear. Property equals responsibility equals prosperity.