PARIS — Paris. THE TREATY on conventional-forces reduction signed yesterday in Paris is a good thing that time has already made obsolete. It is a step in the search to put European security on a new basis, but the threat to security no longer comes from the East but arises from within Europe.
The treaty will bring destruction, or removal from the European theater, of some 100,000 major items of weaponry -- helicopters, tanks, etc. -- and is meant to establish conventional parity between the Warsaw Pact and NATO. However, the United States and the Soviet Union have already lost interest in maintaining even the force levels established in this agreement. The East-West military confrontation has collapsed. The Soviet Union is preoccupied by an internal crisis that steadily becomes worse, the United States by the Persian Gulf, where much of the U.S. equipment being withdrawn from Europe is headed.
The Soviet Union's former chief of staff, Marshal Sergei Akhromeyev, forecasts an end within months to the Warsaw Pact as a military alliance, and its survival as merely an instrument of political consultation. It will be lucky even to do that.
NATO's future may not be that much brighter. It found a new function as mechanism for integrating a united Germany into the new Europe, which in practice meant providing the U.S.S.R. with a rationale for consenting to unification and acknowledging unconditional surrender in the Cold War -- but that now is done.
Without the old military threat from the East, NATO has no solid reason to exist. Efforts to turn it into a Western instrument for ''out-of-area'' interventions have failed. The new security problems inside Europe are not ones NATO can do much about.
The tangible European security problems today are primarily political. First is renewed ethnic and national conflict in the Balkans and the economic crisis produced in the East by the collapse of the command system. But there is something else, of disquieting implications: a perception, inside Western Europe, that danger exists in the new relationships among the European powers themselves, produced by the past year's dramatic events.
This mainly results from Germany's augmented power. France's alliance with West Germany, at the heart of European union, now has seriously been weakened. In Britain the old English sense of threat from the Continent has strengthened.
That issue lies behind the challenge to Margaret Thatcher's leadership of the Tory Party and the government. Her repeatedly expressed fears for the survival of parliamentary sovereignty, and even of ''our beloved queen,'' if European federalists have their way, may be a nonsensical reaction to the actual prospects of federalism. Nonetheless, anxieties about Europe exist in Britain that 17 years' membership in the European Community have failed to still, and which now are rekindled by Germany's re-emergence as Europe's strongest power.
Lifting the Soviet threat has proved a disintegrative force for Europe. The stability imposed by threat is undermined by its removal. Yet there is no serious notion of how to re-create a pan-European assurance of security. Mr. Gorbachev has spoken a European ''common house.'' Whatever that may have meant, it is forgotten today. President Mitterrand of France proposed a European Confederation. Nothing followed.
There is a plan to make the CSCE ''process'' (that's what the Conference on Security and Cooperation in Europe has been until now, a series of meetings) into an institution of European security. Yesterday's Paris meeting sets up a CSCE secretariat in Prague and a ''Conflict Prevention Center'' in Vienna. These no doubt will prove useful, but since the CSCE includes 34 member-states and requires unanimity in its decisions, its ability XTC provide security to any country threatened by another, not to speak of one threatened by irredentist or domestic ethnic conflict, is obviously slight.
Yet means exist for giving the West European allies a renewed conviction of solidarity and purpose, and for bringing the East European democracies into a political community that can reinforce their free institutions and also draw the Balkan states, with all their problems, toward that free community. The CSCE is probably the least important of those agencies.
More useful are the Council of Europe, which demands the rule of law and human-rights guarantees from its members, and has the means to enforce them -- a Human Rights Commission and Court -- and the European Economic Community, which already has acknowledged the need to create new forms of association by which the other European states can be drawn toward the cooperative core of established ''Europe.''
No one seems to be doing much about this. Instead we are seeing a drift away from unity. It is primarily a European problem, not an American one. Nonetheless, failure here will threaten all that the democracies have achieved in common since the 1940s.