Let us begin with a rule of thumb for analyzing international alliances:

When two or more sovereign powers are uncommonly harmonious, it is either because one is able to dominate the others or because all are united against a common enemy.

The story of the Atlantic Alliance fits both parts of the rule. Thanks to its superior economic position the United States has hegemony in the Atlantic Community. And thanks to the Communist threat, the NATO nations have found another good reason to cooperate in the realm of foreign policy.

But time changes even the basis of alliance, and even among so-called status quo powers. The last decade has seen the economic rebirth of Europe and the progressive movement of European states off of the American dole and into the Common Market. The last decade has seen, in short, the weakening of one pillar of the trans-Atlantic structure: American economic hegemony.

The second pillar remains intact. Almost weekly, James Reston uses his column in the New York Times to announce that Premier Khruschchev's belligerent policies are paradoxically strengthening allied unity and building the Atlantic Community.

But opposition to a common enemy is an emphemeral basis for lasting community. When the enemy smiles, the community disappears.

Even with the enemy at the Berlin gates, the sense of community is not unanimous. "A psychology of aloofness has taken hold in much of the free world," Senator Fullbright laments in the latest issue of Foreign Affairs. "Even in Britain the illusion has become widespread, although not in official circles, that somehow the United Kingdom can be neutral in the worldwide power struggle....France has lessened her military participation in NATO and taken other steps which greatly impair the effectiveness of the alliance. Germany adheres loyally to NATO but refuses to accept an obligation commensurate with her wealth and resources ... to carry out the common Western responsibility for assisting the world's underdeveloped nations."

If the U.S. and Europe are in disagreement in time of crisis, what will happen in times of war? It seems very likely that a detente in the Cold War will put new strains on American-European cordiality. If it can happen to Russia and China, it can happen to us.

But will it? American internationalists are seeking to lay the ground for an alliance built on a sense of economic community rather than political fear: The first undertaking is to get the United States to link itself to the Common Market by making the entire trans-Atlantic Alliance a virtual free trade area. At present, Washington is buzzing with debate over what has been called "a minimum step in that direction"--the passage of a new Trade Agreements Act (the present one expires in June) which would empower the President to make across-the-board tariff reductions in negotiations with the European Economic Community.

Other steps have been suggested: a trans-Atlantic monetary agency was the institutional goal offered by Professor Triffin of Yale last year; others have suggested strong multi-lateral initiative be exercised through the Organization for Economic Cooperation and Development (O.E.C.D.); Senator Fullbright has made vague and tentative proposals for institutional solidification of the Atlantic Community.

Fullbright's vagueness is entirely appropriate, for the obstacles even to an Atlantic economic community are formidable. The EEC itself is by no means solidly established. And even if it were there would still be no compelling reason why the United States should fear protectionism from a united Europe. American corporations have already established European "bases," and in any case America does not live or die on its foreign trade.

There is, in sum, no short-run necessity for either liberalization of trade or institutionalized economic cooperation. There is no reason to assume that a large trans-Atlantic community will develop merely because it seems a good thing.

All of which brings us back to Mr. Reston and the thumb-rule. If the United States and Europe are to be joined in the Atlantic Community Fullbright and others envisage, perhaps it will have to be by fear of a common enemy after all.

But the traditional kind of military fear will not do. For, as the new internationalists suggest, economic ties are the basis of a lasting community; military ties of temporary alliance. Thus, if Khrushchev is really intent on bringing Europe and America permanently together, he would be well-advised to intensify his economic offensive--dumping gold, goods, and services on all Western markets. Otherwise, even guarded federalist hopes may prove premature.