I have been an unabashed admirer of Margaret Thatcher since our first meeting shortly after she became leader of the British Conservative opposition in 1975. Never one to waste time on social amenities, Mrs. Thatcher advanced the then startling thesis that the politics of the '70s was all wrong, indeed undemocratic.

The conventional wisdom of the time was that aspirants for office had to contend over some sort of middle way. Mrs. Thatcher would have none of it. If all leaders appeal to the center, she insisted, politics will turn vacuous and, in time, demagogic. The public, not having an effective choice, would make its decision on a basis irrelevant to the real issues. Is it not much better, she argued, to pursue a politics of conviction even if that appears to be extreme? Opponents would then be obliged either to state an alternative or to appear wishy-washy. That way, whatever happened, the public would have a democratic choice.

Dramatic statements by newly elected leaders of the opposition are not unusual. But seeing them put into literal practice is truly uncommon. As Mrs. Thatcher's policy as prime minister evolved, even her most severe critics had to admit that she was driven not by yesterday's public opinion polls but by a passionate desire to shape the public opinion polls of tomorrow. She paid her opponents the ultimate compliment of forcing them into a passionate debate on issues.

It was a mixture of conviction, naivete and strength that enabled Mrs. Thatcher to shape her period as has no other prime minister in this century save the wartime Churchill. She brought about a revolution in British attitudes toward the management of the economy while giving Britain an international voice out of proportion to its economic strength. The measure of her success is shown by the fact that the British Labor Party's official position today is not far from what she inherited as the Conservative position of 1975.

But in the end, Margaret Thatcher's seminal contribution centered on two challenges still to be finally resolved: the future of Western democracy and the nature of the transatlantic relationship.

It is ironic that at the moment of its triumph over Communism, Western democracy should face a crisis of its own, which is much what Mrs. Thatcher described a decade and a half ago. With domestic and international upheavals going far beyond the day-to-day experiences of either citizens or leaders, a nearly irresistible temptation toward demagoguery develops. The search for magic formulae by the electorate is too often encouraged by leaders seeking reassurance in public opinion polls and media reactions.

As a result, the qualities required for reaching office no longer bear a necessary relationship to the qualities needed for governing. Any democratic leader must have sensitive antennae for the public mood. But in the end, a leader will be judged by how well he performs his ultimate role of taking his society from where it is to where it has never been. This is why the public does not forgive its leaders for debacles, even if they are caused by following conventional wisdom.

The art of democratic leadership resides in judging correctly how far ahead of the conventional wisdom it is safe to be. If a leader confines himself to what is generally understood, he dooms his society to stagnation and himself to eventual irrelevance. But if he gets too far ahead, he will suffer shipwreck.

This is a process with its built-in terminal point. Even when a remarkable leader navigates this passage -- as Mrs. Thatcher did for an unprecedented three elections -- a point of exhaustion is reached by both the bureaucracies and the public. For the bureaucracies because they are, after all, run by experts relying on their knowledge of the familiar, growing increasingly restless as their conventional wisdom is under assault. And even the most tolerant electorate sooner or later runs out of patience with being jolted into new effort, especially if reform moves into ever more esoteric fields.

Not surprisingly, Mrs. Thatcher's successors have pledged a consensus style of government. But I hope this reflects no more than the desire for a respite. If democracy is to thrive, Mrs. Thatcher's faith in the power of reason and the importance of a clash of ideas must be key elements. Within a measurable time the issues that led to Mrs. Thatcher's downfall will be forgotten or appear inconsequential. What is left will be the memory of her commitment to a major role for her country and her faith in its adaptability to the challenge of modernity -- qualities needed if Britain is to continue to master its future.

Americans have a special reason to remember Mrs. Thatcher with affection and gratitude. For she was a great exponent of the special relationship between Britain and the United States that has been so crucial in shaping the postwar world. Some on both sides of the Atlantic sneer at these ties as relics of a wartime partnership long since overtaken by events. Periodically -- as at the beginning of the Bush administration -- the argument is heard that America should shift its emphasis from Britain to more powerful members of the Atlantic alliance.

But an alliance is more than a set of statistics. It requires strength, to be sure, but it must be coupled with the intangibles of reliability, character and historical experience. Were Britain to abandon its historic identity, America would lose one of the stabilizing elements in its own policy. For as the Atlantic alliance is declining in the security field, the challenge for both Europe and the United States becomes how to develop transatlantic relationships relevant to the post-Cold War period.

During the entire postwar period, America has applied its missionary zeal and its problem-solving energy to promoting European integration almost as an end in itself. The commitment was idealistic. But the assumption on which it was based -- that an integrated Europe would automatically cooperate with the United States -- flew in the face of historical experience. America grew too accustomed to the devastated, temporarily impotent Europe of the postwar period. It forgot -- if it ever knew -- the Europe that had launched the industrial revolution, invented the concept of national sovereignty and operated a complex balance of power based on shifting alliances for three centuries. It was naive to take for granted that a unified Europe would automatically help carry American burdens and that it would continue to follow American global prescriptions as it had in the early postwar years of European dependency. A Europe reasserting its traditional personality was bound to seek to redress its balance of influence with the United States.

The virtue of the special Anglo-American relationship was that it helped bridge this gap between American moral absolutes, which equated foreign policy with universal principles, and Europe's ethical egoism, which assumed that what was good for the nation was best for the rest of the world. In Britain's case there was some merit to this belief. For Britain at the height of her power practiced it with an innate moderation that frequently justified the presumption. In the 19th century, British policy was perhaps the principal factor in a European system that kept the peace for 99 years without a major war.

The key issue in Atlantic relations is not whether Britain will join Europe -- that is substantially settled, except for details. The challenge is to avoid both American isolationism and a European nationalism that defines its identity by way of confrontation with America. A creative solution is crucial for both sides of the Atlantic. A narrowly conceived Europe would sooner or later consume itself in its own divisions or overreach in its own ambitions. An open Europe is in the self-interest of America, for it is beyond America's psychological or physical capacity to be the sole center of initiative and responsibility in the non-Communist world.

The solution is not to sacrifice the special intimacy of the Anglo-American relationship on the altar of the European idea, but rather to replicate it on a wider plane of America's relations with all its European allies. The European nations must decide what precise structure is appropriate for the European Community. But the special frankness that originally served as compensation for a disparity of power is even more essential in the new partnership of equals. A new definition of Atlantic relations is needed as Europe edges toward identity and America toward a foreign policy with which Europeans have always been familiar: as one country among many, unable either to dominate the world or escape from it, sensitive to shifts in the balance of power.

Mrs. Thatcher instinctively grasped the importance of this transition. She might hector the United States, but she asked the right questions even when one disagreed with some of her answers. She did not want a Europe run by bureaucrats; she feared a resurgence of the statism that had been overcome by recent market revolution. In her mind, the slogans of a Europe from the Atlantic to the Urals threatened to wind up excluding the United States and Canada, while reawakening a Central European nationalism seemingly transcended after two world wars. She sought to anchor Europe with North America before she irrevocably committed Britain to a European role. And it cannot be in America's interest to cause this effort to fail. For a sense of impotence in Britain is likely to drive the country toward a restrictive version of Gaullism conducted with subtle and indirect British methods.

The details of such a design for Europe are for another occasion. For now, it is well to remember a gallant leader who believed that in the end nations and individuals are not products of circumstance but can shape their futures by their commitment. In that sense, all freedom-loving people have to hope that Mrs. Thatcher marked the beginning of an era and not its end.