Today's lesson: Why paying down the debt is good for Social Security (and the rest of the government, too).

George W. Bush feels those projected federal budget surpluses burning a hole in his pocket. And he wants to do away with them as quickly as possible, with big tax cuts. Some of my liberal friends feel a similar sensation. They've charged Clinton and Gore with pursuing a Coolidge-like economic strategy that would prioritize paying down the debt over bold new spending. But there are good liberal reasons for making debt reduction our first priority, at least for now.

For one thing, in a full employment economy, paying down debt is good Keynesian countercyclical macroeconomic policy, which will help sustain long-term growth. Throwing gasoline on the hot economy by increasing spending or cutting taxes runs the risk of re-igniting inflation and forcing the Federal Reserve to hike interest rates.

Equally important, reducing debt now means more public money will be available in the future. Imagine two people with identical earnings--one spends everything right away and the other saves 20 percent. Over a 20-year period, the saver will enjoy 20 percent less consumption for the first 10 years, but have 40 percent or so more available over the next 10. (Anti-government activists, who dominate the Bush team, understand this simple truth. Liberals, even of the big-spending variety, should take note of it, too.)

Thanks to Ronald Reagan's borrow-and-spend legacy, interest on the debt will be $284 billion this year, counting the $60 billion that goes to the Social Security trust funds. That means that one of every five dollars the government spends on everything but Social Security goes to paying interest. If those interest obligations can be sharply reduced, we'd free up very large sums to use more productively in the future (for dealing with Social Security's upcoming long-term shortfall, for instance).

Under the latest official projections, Social Security payroll taxes will cover benefit payments until 2015. At that point, Social Security will have to start using some of the interest it receives from the government to pay benefits. After 2025, Social Security will begin cashing in the government IOUs in the trust funds to maintain benefits. (By 2037, it is predicted, the trust funds will be exhausted.)

When Social Security starts spending its interest earnings, that will transform the interest that the government pays to Social Security from a bookkeeping entry to a real cost. And when Social Security starts dipping into principal, the problem will be compounded. But if interest on the national debt has been slashed, it will be much easier to meet those future obligations without higher taxes or benefit cuts. In other words, debt reduction is a straightforward and effective way to "save Social Security," just as President Clinton says.

To sing the praises of debt reduction does not mean we should shut down the entire government for a few years to eliminate the national debt. Obviously, there has to be a balance between meeting current needs and planning for the future. Nor is sustaining Social Security the only issue. Reducing the national debt now will help us maintain or enhance other government services down the road--because we won't be wasting so much money on interest payments. But the combination of our current happy economic circumstances and our upcoming needs offers a strong case for making debt reduction one of our highest priorities right now.