If there ever was a sure thing, a hard fact in political life, it is that no country can indefinitely spend $200 billion more than it takes in. Not even the United States. No matter how starry-eyed your belief in supply-side nostrums or Laffer curves, no matter how fervently you worship at the temple of growth, you have to concede that at a certain point the bills come due or the lenders lose confidence, or both.

It doesn't help to put things in percentage GNP terms. Five percent of GNP sounds better than 200 billion dollars, but it is an improvement in sound only. Five percent compounded yearly makes for a debt no less malignant.

This is all so obvious that it is no longer a very interesting question whether such deficits stretching as far as the eye can see will bring ruin. The only interesting question is how a political system can look ruin so plainly in the eye and do nothing about it.

There is no shortage of explanations: A stubborn president, allergic to taxes and prepared to mortgage the economy to pay for the allergy. A Democratic Party, intellectually shipwrecked and clinging desperately to Social Security while waiting for a new idea to float by. A political system ingeniously constructed 200 years ago to check and balance and foil a (potentially tyrannous) majority and, when it comes to foiling, working perfectly.

These explanations are plausible as far as they go, but they don't quite satisfy. Even for a system as fractured, partisan and rigid as ours, it is hard to understand so fatal a dissociation from so obvious a threat. Something else is going on.

That something else is the extraordinary safety of American life and the habits of thought such safety breeds. There is a kid of bedrock belief that while catastrophe can happen, it cannot happen here. This is not classical American optimism, now resurgent, the feeling that things necessarily will get better. It is a variant, the feeling that here things simply cannot fall apart.

Safety is so pervasive a feature of American life that it has become invisible to us. It takes a foreigner to see it. "You live so very safely here," said South African novelist Nadine Gordimer on a recent visit to Washington. "To make a protest and be arrested for a couple of hours can make you a hero. In my country it's quite different."

Indeed. And in our country, one grows to believe not just that the individual is inviolable, but the nation too. It is no mystery why. There is safety in American numbers: a quarter of a billion people, a $4 trillion economy, two vast oceans for protection, two weak and friendly countries for neighbors. This is, after all, a land on which the last war to be fought ended 120 years ago.

Czech novelist Milan Kundera once defined a small nation as "one whose very existence may be put in question at any moment. A small nation can disappear and knows it." Czechoslovakia and Israel, for example, are small nations. The United States, by this definition, is a very large one. For a great power -- a superpower -- existence is never the issue. Its worries are about interests. And interests, in the end, are disposable. Vietnam or Lebanon can disappear from the American horizon, leaving everyday life (here) unchanged. Large countries have large margins of error. They know failure, but not disaster.

Security is not just a question of geography and size, but of wealth. In economic life, the safety of the American system is legendary. The whole world comes here to invest because it considers our system so stable and our currency so safe. That makes for a certain carelessness. The U.S. economy is such an enormously productive engine that it can sustain staggering waste. Two weeks ago the House voted to foreclose on synfuels, at a loss of $2 billion. A $4.5 billion nuclear plant lies completed and unused on Long Island because the surrounding county has had second thoughts about the idea. For the American economy such gigantic blunders amount to spillage.

Of course, we have not totally escaped disaster. There was, after all, the Depression. But so long ago that most of us are too young to remember it and the president is old enough to have forgotten it. Memory fades. It's morning in America. We have a president with a sunny disposition, even happier luck -- neither falling oil prices, nor overextended Russians, nor even Paul Volcker are his creations -- and the unshakable conviction that Providence has taken us in hand.

Catastrophe is for smaller, less virtuous countries. No hurricanes at the city on a hill. Here it is safe. Not even $200 billion deficits can shake that faith. Indeed, it is that faith that makes such deficits possible.

On American safety, Gordimer added, "I don't sneer at it. It's an enviable kind of innocence." Innocence it is. Enviable it may not prove to be.