The Big Mac Principle explains a lot going on in Washington these days.

The Big Mac Principle coined here for the first time, is not an original idea, but simply a restatement of an old truth: the whole is equal to more than the sum of its parts.

That's the principle running forward, but the axiom also runs backward. In this direction, it means: the whole is equal to less than the sum of its parts.

Anyone can understand the relationship of these truths to the real-life Big Mac. A Big Mac. of course, is "two all-beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun." Depending on your taste, these few ingredients produce one of the magnificent gastronomical delights of American civilization (the whole is equal to more than the sum of its parts) or an insult to the sensitive stomach (the whole is equal to less than the sum of its parts).

Having grasped the Big Mac Principle, you can now begin to apply it.

Economists, for example, can't agree whether inflation is the Big Mac Principle running forward or backward. One school believes that all the little price increases threaten to evolve into a monster, sowing social conflict among classes and, ultimately, threatening democracy with a mass of controls. These economists would risk a long period of slow growth to avoid this dreaded outcome.

But another school of economists think that inflation is an exaggerated evil. They would be rid of it, but point out that people have learned to live with it. They are unwilling to take the painful cure for inflation, because they fear that the medicine - high unemployment - may be worse than the disease, risking social and political turmoil.

In short, the Big Mac Principle explains the fundamental division - a division based mostly on social values and temperament - among economists today. If they could decide whether inflation's collective danger is more (or less) than all the individual price increases, professional agreement would be much greater than it is.

This confusion, though, is rare. Usually, it's remarkably easy to tell which version of the Big Mac Principle is operating. In Washington, for example, the principle almost always works in reverse.

Take Congress. Today's Members are younger, better-educated and harder-working than their predecessors. Yet, is Congress producing better legislation, gaining public confidence and improving the functioning of government?

Precisely the opposite. The evidence suggests that Congress continues to sink in public esteem, government functions with increasing creakiness and the current out-pouring of legislation is, if no worse than what came before, certainly no better.

This should surprise no one. One of Congress's major problems today is that its Members are younger, better-educated and harder-working than their predecessors. In fact, they work too hard. Everyone wants to be a star; everyone wants to lead, and nobody wants to follow.

Consequently, Congress has experienced a proliferation of committees and subcommittees to accommodate the expectations of its new Members. This multiplication contributes substantially to the creakiness of government.

First, it makes it difficult for bureaucrats and Cabinet members to do their work because they spend so much time testifying on the Hill. Second, it produces more and more contradictory legislation, with the conflicts left to be resolved by lawyers and lawsuits; this adds to court congestion and intensifies inflation by raising legal costs.

Nor is that all. Because the new crop of Senators and Representatives are better educated than their elders, they don't take well to discipline. This explains much of the legislative chaos of the last few years. Even the most astute congressional leadership might not be able to control this mob, but the leadership is less than the best. Consequently, the disparity in abilities only fans the frustrations of younger Members and increases their inclination to rebel.

Indeed, the quickest way to improve Congress would probably be to elect more lazy, mediocre Members who would look after their constituents and play follow the leader.

Next we come to Jimmy Carter. Here, too, is a sad example of the Big Mac Principle working in the reverse.

Anyone reading Carter's resume might easily conclude that he is the best-qualified man to occupy the office this century. He has a keen intelligence and, unlike most of his predecessors, his experience before moving into the White House was wide and varied: a nuclear engineer, businessman, local politician and governor. In addition, his party controls Congress, and he comes from the fastest expanding part fo the country, the South.

What these impressive personal and political assets have produced is a floundering presidency.

The contradiction lies in Carter himself. All his dazzling personal attributes are neutralized by flaws that stem from his very strengths. He believes to much in himself and has kept to himself more decision making than anyone can possibly handle.

Carter cheats himself. In his obsession with detail, he has failed to define broad themes for his Administration. By not delegating more to subordinates - and creating independent power bases within his Administration - he has actually left himself more vulnerable to manipulation by subordinates. He forgets that what he decides on Issue B may conflict what he previously decided on Issue A. The result is confusion and loss of confidence, at home and abroad.

The contrast with Jerry Ford is inescapable. Even Ford's admirers rarely claim that he is anything more than a nice guy, but he had the sense to delegate responsibility for major areas of policy - foreign affairs, the economy - to trusted subordinates. He left to himself major political decisions and the resolution of fundamental disagreements. On the record so far, history will judge the man of lesser abilities the better President.

Ford is the Big Mac Principle going forward; Carter is the principle going backward. But he shouldn't despair. Maybe if he changes his specail sauce, he can change direction too.