BY ALL INDICATIONS, the economic summit meeting beginning today in Williamsburg will be a polite affair. The leaders of the world's seven largest industrial nations are expected publicly to reaffirm their allegiance to arms control, worldwide economic growth--and not much else.

There are, of course, many contentious issues that the participants could talk about. President Reagan, for example, might like to drum up support for his Central American policies and to urge greater restraint in trading with the communist bloc. French President Mitterrand would like to press for a return to fixed exchange rates which, he hopes, would protect the franc from the embarrassing devaluation that his domestic policies have produced.

The precarious situation of the Third World debtor countries is also on everyone's list. But dealing with that would bring up the tricky question of mounting protectionism among the industrial countries. It would also highlight the need for lower U.S. interest rates to reduce the strain of debt service on the developing nations, put the dollar on a more reasonable basis vis-Ma-vis other currencies and provide a stronger U.S. lead for worldwide recovery. But that, of course, would bring up the issue of the U.S. budget deficit-- which President Reagan would rather not talk about.

Japanese Prime Minister Nakasone would like to rebut his country's image as the bad boy of world trade. He might point out that much of Japan's competitiveness arises not from government subsidies, but from the discipline of its workers, the creativity of its industrial designers and its superior control over domestic inflation. He might also note that he would like to stimulate Japanese domestic consumption and deemphasize foreign markets, but this would require further reducing Japanese interest rates. And as long as other countries' interest rates stay high, to do so would simply devalue the yen and make Japanese exports still more competitive.

Then there is the matter of the millions of unemployed people in Europe and the United States. It's on everyone's mind, but no one knows what to do about it except join hands and pray for the world economic recovery that might ease this and many other problems.

There is, of course, a strong element of unpredictability about any meeting in which the leaders of the Western World sit down to talk unprotected by coteries of aides. Perhaps the 4,000 or so media people gathered there will find more of interest to report than the charm of Williamsburg's idealized view of the American colonial past or the quality of the shoofly pie and deep-fried hush puppies. But for all the hype, economic summits have value beyond their immediate outcome. They are an occasion for the leaders of the West to educate and remind themselves that the consequences of their domestic policies now extend well beyond their own borders.