''America was thus clearly top nation, and history came to a .'' - W. C. Sellars, R. J. Yeatman, 1066 And All That

Francis Fukuyama's celebrated restatement of Sellars and Yeatman's (not to mention Hegel's) thesis in the summer issue of the National Interest - that we have reached ''the end of history,'' now that the debate over the highest form of human government has been resolved in favor of democracy - has sparked a frisky debate among scholars.

The piece is notable not so much in itself, but as a reflection of the spirit of the age. Can it really be only five years since Jean-Francois Revel wondered whether democracy was not a ''brief parenthesis that is closing before our eyes?'' And now it's ''the end point of mankind's ideological evolution.''

So much has gone right lately, we seem suddenly to have emerged into a dazzling new era. As we approach the year 2000, the Western world has been seized by a new millenarianism, a burst of boundless optimism about humanity's chances after decades of fear and uncertainty. It is not only the rise of democracy that we herald, but its inevitable and universal triumph, and not only of democracy, but of peace, prosperity, global equilibrium.

Oddly, this utopianism is often expressed in the course of announcing the end of utopianism, the vision of humanity reborn underlying the totalitarian ideal. ''The triumph of the twentieth century is that it has purged itself of certainty,'' says the Economist, with its usual certainty.

REVOLT AGAINST GENES

''We have now entered the age of humility,'' writes Richard Davy in the Independent, which means no less than a ''fundamental shift in human consciousness,'' promotion ''in the great school of life.'' International affairs columnist Gwynne Dyer even speculates that mankind is in the midst of an epochal ''revolt against the genes,'' casting off its genetic predisposition to tribal conflict.

It is easy enough to extrapolate a utopia from recent events. Consider:

Since 1973, at least two dozen countries have gone all or most of the way down the road from dictatorship to democracy: Greece and Turkey; Portugal and Spain; Bolivia, Peru, Argentina, Uruguay, Brazil, Guatemala, Honduras; Grenada and the Philippines, if not Haiti; and, depending on your politics, El Salvador, Nicaragua, and South Korea.

Democracy is now in sight in Mexico, Hungary and Poland; something close to it even appears possible in the unlikely soil of Chile, South Africa, and the U.S.S.R. The percentage of the world's population classified as living in ''free'' countries by Freedom House last year reached 38.3%, double what it was in 1975. For the first time in history, more people live under democracy than any single other form of government.

The major developed countries have been at peace for longer now than at any time since the Roman Empire: 44 years, as of Sept. 2, eclipsing the previous record of almost 39 years between Waterloo and the Crimean war. This is connected with the spread of democracy, for it is a truth that free peoples will not wage war on one another: they have not in this century, certainly.

The political scientist John Mueller suggests in Retreat from Doomsday this is the result neither of chance nor deterrence, but of choice: the world, or at least the developed world, has simply decided to abolish war, as once it abolished slavery and dueling.

At 81 months, the current U.S. economic expansion is the longest ever in peacetime, and more than twice as long as the postwar average. Some economists now argue that increased adaptability in the real economy - smaller inventories, steady demand for services, globalization - and heightened sensitivity to inflation in the bond markets make the economy almost ''recession-proof.''

At the same time, after two centuries of industrialization in which little or no regard was paid to the environmental costs, the major economies are finally starting to redress the balance between growth and conservation. The economics are not new, but the politics of ''sustainable development'' are unprecedented. Why, it's almost . . . rational.

Under the circumstances, it's hardly surprising that utopian ideals should flourish. A European currency? Let's make it global. Awed by Voyager's pass by Neptune? Let's plant gardens on Mars.

How sound is the new millenarianism? And what can sustain its momentum? These can wait until next week; the millenium, after all, is still 11 years away.