A tale of two economies.

The first commandment of economics is: Grow; grow forever. Companies must get bigger. National economies need to swell by a certain percentage each year. People should want more, make more, earn more, spend more -- evermore.

The first commandment of the Earth is: Enough. Just so much and no more. Just so much soil. Just so much water. Just so much sunshine.

Everything born of the Earth grows to its appropriate size and then stops. The planet does not get bigger; it gets better. Its creatures learn, mature, diversify, evolve and create amazing beauty and novelty and complexity, but they live within absolute limits.

When there's an inconsistency between human economics and the laws of planet Earth, which do you think is going to win?

Economics says: Compete. Only by pitting yourself against a worthy opponent will you perform efficiently. The reward for successful competition will be growth. You will eat up your opponents, one by one, and, as you do, you will gain the resources to do it some more.

The Earth says: Compete, yes, but keep your competition in bounds. Don't annihilate. Take only what you need. Leave your competitor enough to live. Wherever possible, cooperate. Pollinate each other, create shelter for each other, build firm structures that lift smaller species up to the light. Pass around the nutrients, share the territory. Some kinds of excellence rise out of competition; others rise out of cooperation. You're not in a war. You're in a community.

Which of those mandates makes a world worth living in?

Economics says: Use it up fast. Don't bother with repair; the sooner something wears out, the sooner you'll buy another. That makes the gross national product go 'round. Throw things out when you get tired of them. Throw them to a place where they become useless. Grab materials and energy to make more. Shave the forests every 30 years. Get the oil out of the ground and burn it. Make jobs so people can earn money, so they can buy more stuff and throw it out.

The Earth says: What's the hurry? Take your time building soils, forests, coral reefs, mountains. Take centuries or millennia. When any part wears out, don't discard it, turn it into food for something else. If it takes hundreds of years to grow a forest and millions of years to compress oil, maybe that's the rate at which they ought to be used.

Economics discounts the future. Ten years from now, $2 will be worth only $1. You could invest that dollar at 7 percent and double it in 10 years. Take it now. Turn it into dollars.

The Earth says: Nonsense. Those invested dollars grow in value only if something worth buying grows, too. The Earth and its treasures will not double in 10 years. What will you spend your doubled dollars on if there is less soil, less oil, dirtier water, fewer creatures, less beauty?

The Earth's rule is: Give to the future. Lay up a fraction of an inch of topsoil each year. Give your all to nurture the young. Never take more in your generation than you give back to the next.

The economic rule is: Do whatever makes sense in monetary terms.

The Earth says: Money measures nothing more than the relative power of some humans over other humans, and that power is puny compared to the powers of climate, oceans and uncounted multitudes of one-celled organisms that created the atmosphere, that recycle the waste, that have lasted for 3 billion years.

The fact that the economy -- which has lasted for maybe 200 years--puts zero value on these things means only that the economy knows nothing about value -- or about lasting.

Economics says: Worry, struggle, be dissatisfied. The permanent condition of humankind is scarcity. The only way out of scarcity is to accumulate and hoard, though that means, regrettably, that others will have less. Too bad, but there is not enough to go around.

The Earth says: Rejoice! You have been born into a world of self-maintaining abundance and incredible beauty. Feel it, taste it, be amazed by it. If you stop your struggle and lift your eyes long enough to see Earth's wonders, to play and dance with the glories around you, you will discover what you really need. It isn't that much. There is enough. As long as you control your numbers, there will be enough for everyone and for as long as you can imagine.

We don't get to choose which laws--those of the economy or those of the Earth--ultimately will prevail. But we can choose which ones we personally will live by--and whether to make our economic laws consistent with planetary ones.

Or to find out what happens if we don't.

Donella Meadows is an adjunct professor at Dartmouth College. Reprinted from her syndicated column, "The Global Citizen."