Invention is the mother of necessity.

This is obvious.

Who needed the light bulb before Edison invented it? (The midnight oil burned fine, thanks.) Did college kids slouch all surly around campuses on spring days, waiting for the Wham-O company to bring them frisbees?

Inventions do not save work, they make it. Why do we keep thinking they'll ease the load? Give the police department a computer to run parking tickets through, and all of a sudden policemen are putting Denver boots on cars, stalking the owners into their offices, demanding cash. Everything comes out equal. No net gain. Maybe even a loss.

"Freedom From Want." Who was Franklin Roosevelt kidding? Supply in this country has rarely been the problem. It's demand we demand, and so inventors give it to us. The trick in a recession is stimulating demand, not supply, and one of the great political inventions of the century, Keynesian economics, is aimed at doing just that. The game is not mousetraps, but worlds beating paths to the door. If you think it's the other way around, you'd have had Alexander Graham Bell stop working when he'd built one telephone. Invention - which is to say wanting, dreaming, hitching wagons to stars - is the American way. It's our totem, a blazon, an icon. We should replace the stars and stripes on our flag with a light bulb, the one that cartoonists have flashing over the heads of inventors, such as Gyro Gearloose in Walt Disney Comics.

Invention is the stuff of politics and Washington is a city which will exist only as long as our government continues to invent needs for itself to exist.For instance, Richard Nixon invented the New Frontier, so we'd all need to head out for it. (He wanted to "get the country moving again.") Harry Truman invented the Do-Nothing Congress. Lyndon Johnson invented the Great Society. Harry Anslinger invented marijuana-as-killer-weed. Like Ford with the automobile, Joe McCarthy perfected assembly-line production of inventions including fellow travellers, Communnists, Comsymps, Commie dupes, pinkos and so on. Anita Bryant invented homosexuality as a national issue, or homosexuals invented Anita Bryant as a national issue, but clearly they needed each other, and that's the point.

Other important political inventions: little old ladies in tennis shoes; creeping socialism; the five kinds of liberals (mealy-mouthed, limousine, armchair, knee-jerk and bleeding-heart); and the four powers (black, brown, red and gay).

Politicians and governments need to be needed. George III could have left it alone when the Declaration of Independence said we didn't need him. Instead, he sent in the troops, and invented the American Revolution. Look how upset we got at the Whiskey Rebellion, the Civil War, and now it's the Indians saying they don't need us on their ancestral lands.

This is serious business.Our whole system of government, for instance. Says Richard Cole, political science professor at George Washington University, "Federalism was totally new in 1787. It was an accident. They didn't know what they'd invented. It was a compromise between the centralists and the people who wanted the power more diffused. But a division of power between a national government and its subunits was previously unheard of." And previously unneeded, one might add.

Sidney Fine, professor of history at the University of Michigan, cites the invention of a Supreme Court which can overrule legislation. Other countries, such as England, have their final say in their legislatures. It's also difficult to imagine life without another American invention, the anti-trust laws, Fine says. Then there's the TVA, and environmental impact statements, the National Labor Relations Act, all of which make us need government the more.

Eric Goldman, Rollins professor of history at Princeton, notes that foreign aid was invented in 1940 with the Lend-Lease program. "There'd been nothing like it before." A decade later, foreign aid was a key prop to the doctrine of containment of Communism. We needed people to need us.

Other important political inventions: male chauvinist pigs; the China lobby; roving bands of angry Negro youths; the Protocols of the Elders of Zion; the fireside chat; juvenile delinquency and all the bigs (big oil, big money, big medicine, big labor).

But the one a lot of political scientists and historians seem to agree on is an invention which got none of the ceremonies and media send-off of, say, the Peace Corps or the United Nations. The concept is sometimes called an "executive secretariat," or a "general staff." It's what we think of now simply as the White House, all those hundreds of special assistants, National Security Council members, the Council of Economic Advisers and all their staff picking up telephones everyday and saying: "The president wants . . . "

"It's almost a fourth branch of government," says Eric Goldman. "It functions through the other branches because of the power of saying 'The president wants.' It has diminished the Cabinet considerably. It's much more important to get a call from Hamilton Jordan than from a member of the Cabinet. A Cabinet officer is most important when he functions as White House staff, like John Mitchell or Bobby Kennedy."

There were key moments in the creation of this fourth branch - the centralizing of the budget into the Bureau of the Budget in 1921. And the Brownlow report, which proposed aiding Franklin Roosevelt with staffers who had "a passion for anonymity." Trevor Depuy, a military historian, says that General George C. Marshall brought the concept to the Pentagon in World War II, quietly imitating the German general staff, and that Eisenhower brought it to maturity in the White House. In any case, it made possible the exquisite subtleties of Watergate. And for all our bad memories of Haldeman's abuses of power, President Carter has been attacked for not appointing his own chief of staff. We need one. Otherwise we wouldn't have invented one. Or is it the other way around?

Let's see, if mothers are the necessity of inventors, then . . .