PRESIDENT BUSH is in Paris today for a summit of the Conference on Security and Cooperation in Europe. This ambitiously named organization -- actually, it's not an organization but a process, a floating conference -- brings together 34 countries: everyone (including the United States and Canada) in NATO, everyone from the all-but-extinct Warsaw Pact, the neutrals. CSCE was created in 1975 for the uphill work of promoting human rights across a hermetic East-West line. It found itself a roaring surprise success, custodian of the hottest issue of the transitional '80s and the single inclusive pan-European institution available to greet the post-Cold War '90s. With no headquarters or staff, it developed an anti-bureaucratic quality that distinguished it from the formal, functional, exclusive European organizations already in being. These credentials made it the natural place for many Europeans to turn when they began looking for ways to organize the new peace.

The CSCE summit is being spoken of as a triumphal post-Cold War coming-out party for a Europe that is becoming both "a common home" (Mikhail Gorbachev) and "whole and free" (George Bush). A splendid East-West treaty is being delivered on schedule; it reduces conventional arms in Europe in a way that eliminates the old threat of Soviet attack. A solemn nonaggression declaration will be made. Amid much talk of endowing it with pan-European security responsibilities, CSCE will set up its first headquarters and permanent staff (in Prague), create procedures for regular high-level consultations and establish a "conflict prevention center."

Western Europe hopes CSCE will treat new-era concerns like ethnic disputes, migrations and ecological disasters. Eastern Europe is pleased to join such a congenial continental forum. The Soviet Union, a bit nervous to be shorn of its old alliance and regional buffer, sees CSCE as its principal ticket to Europe. Still, it's necessary to keep in mind that CSCE's experience so far is mostly in human rights. It has no standing yet in conflict resolution, crisis management or other security matters. It comes with none of the tested heavy-duty mutual obligations that NATO members offer each other.

The United States is sometimes suspected of preferring a familiar backward-looking military organization that it runs, NATO, to an experimental forward-looking political process in which its primacy will likely be vitiated, CSCE. But NATO is more than a relic of the Cold War, more than an instrument of American hegemony. It is a proven vehicle for a stabilizing American engagement in Europe. NATO needs to be redefined but not dismissed. The United States is right to insist that, as Europe searches for useful new institutions, it should not casually weaken useful old ones.