Here is one optimist's reason for believing unity will prevail over disunity, integration over disintegration. In fact, I'll bet that within the next hundred years (I'm giving the world time for setbacks and myself time to be out of the betting game, just in case I lose this one), nationhood as we know it will be obsolete; all states will recognize a single, global authority. A phrase briefly fashionable in the mid-20th century--"citizen of the world"--will have assumed real meaning by the end of the 21st century.

All countries are basically social arrangements, accommodations to changing circumstances. No matter how permanent and even sacred they may seem at any one time, in fact they are all artificial and temporary. Through the ages, there has been an overall trend toward larger units claiming sovereignty and paradoxically, a gradual diminution of how much true sovereignty any one country actually has.

The forerunner of the nation was a prehistoric band clustered around a fire beside a river in a valley. It's members had a language, a set of supernatural beliefs and a repertoire of legends about their ancestors. Eventually they forged primitive weapons and set off over the mountain, mumbling phrases that could be loosely translated as having something to do with "vital national interests" and a "manifest destiny." When they reached the next valley, they massacred and enslaved some weaker band of people they found clustered around some smaller fire and thus became the world's first imperialists.

Empires were a powerful force for obliterating natural and demographic barriers and forging connections among far-flung parts of the world. The British left their system of civil service in India, Kenya and Guyana, while the Spaniards, Portuguese and French spread Roman Catholicism to almost every continent.

Empire eventually yielded to the nation-state, made up primarily of a single tribe. China, France, Germany and Japan are surviving examples. Yet each of them too is the consequence of a centuries-long process of accretion. It took the shedding of much blood in many valleys for Normandy, Brittany and Gascony to become part of France.

Today fewer than 10% of the 186 countries on earth are ethnically homogeneous. The rest are multinational states. Most of them have pushed their boundaries outward, often until they reached the sea. That's how California became part of the U.S. and the Kamchatka Peninsula part of Russia.

The main goal driving the process of political expansion and consolidation was conquest. The big absorbed the small, the strong the weak. National might made international right. Such a world was in a more or less constant state of war.

From time to time the best minds wondered whether wasn't a hell of a way to run a planet; perhaps national sovereignty wasn't such a great idea after all. Dante in the 14th century, Erasmus in the 16th and Grotius in the 17th all envisioned international law as a means of overcoming the natural tendancy of states to settle their differences by force.

In the 18th century the Enlightenment--represented by Rousseau in France, Hume in Scotland, Kant in Germany, Paine and Jefferson in the U.S.--gave rise to the idea that all human beings are born equal and should, as citizens, enjoy certain basic liberties and rights, including that of choosing their leaders. Once there was a universal ideology to govern the conduct of nation toward one another. In 1795 Kant advocated a |"peaceful league of democracies".

But it has taken the events in our own wondrous and terrible to clinch the case for world government. With the advent of electricity, radio and air travel, the planet has become smaller than ever, its commercial life freer, its nations more inter-dependent and its conflicts bloodier. The price of settling international disputes by force was rapidly becoming too high for the victors, not to mention the vanquished. That conclusion should have been clear enough at the battle of the Somme in 1916; by the destruction of Hiroshima in 1945, it was unavoidable.

Once again great minds thought alike: Einstein, Ghandi, Toynbee and Camus all favored giving primacy to interests higher than those of the nation. So, finally, did the statesmen. Each world war inspired the creation of an international organization, The League of Nations in the 1920's and the United Nations in the '40s.

The plot thickened with the heavy breathing arrival on the scene of a new species of ideology--expansionist totalitarianism--as perpetrated by the Nazis and the Soviets. It threatened the very idea of democracy and divided the world. The advocacy of any kind of world government became highly suspect. By 1950 "one-worlder" was a term of derision for those suspected of being wooly-headed naïfs, if not crypto-communists.

At the same time, however, Stalin's conquest of Eastern Europe spurred the Western democracies to form NATO, history's most ambitious, enduring and successful exercise in collective security. The U.S. and the Soviet Union also scared each other into negotiating nuclear-arms-control treaties that set in place two vital principals: adversary states have a mutual interest in eliminating the danger of strategic surprise, and each legitimately has a say in the composition of the other's arsenal of last resort. The result was further dilution of national sovereignty and a useful precedent for the management of relations between nuclear-armed rivals in the future.

The cold war also saw the European Community pioneer the kind of regional cohesion that may pave the way for globalism. Meanwhile, the free world formed multilateral financial institutions that depend on member states' willingness to give up a degree of sovereignty. The International Monetary Fund can virtually dictate fiscal policies, even including how much tax a government should levy on its citizens. The General Agreement on Tariffs and Trade regulates how much a nation can charge on imports. These organizations can be seen as the proto-ministries of trade, finance and development for a united world.

The internal affairs of a nation used to be off limits to the world community. Now the principal of "humanitarian intervention" is gaining acceptance. A turning point came in April 1991, shortly after Saddam Hussein's withdrawal from Kuwait, when the U.N. Security Council authorized allied troops to assist starving Kurds in northern Iraq.

Globalization has also contributed to the spread of terrorism, drug trafficking, AIDS and environmental degradation. But because those threats are more than any one nation can cope with on its own, they constitute an incentive for international cooperation.

However limited its accomplishments, last month's Earth Summit in Rio signified the participants' acceptance of what Maurice Strong, the main impresario of the event, called "the transcending sovereignty of nature": since the by-products of industrial civilization cross boarders, so must the authority to deal with them.

Collective action on a global scale will be easier to achieve in a world already knit together by cables and air waves. The fax machine had much to do with the downfall of tyrants in Eastern Europe. Two years ago I was assigned an interpreter in Estonia who spoke with a slight southern accent because she had learned English watching Dallas, courtesy of TV signals beamed over the border from neighboring Finland. The Cosby Show, aired on South African television, has no doubt helped erode apartheid.

The ideological and cultural blending strikes some observers as too much of a good thing. Writing in the Atlantic, Rutgers political scientist Benjamin Barber laments what he calls "McWorld." He also identifies the countertrend, the re-emergence of nationalism in its ugliest, most divisive and violent form.

Yet Azerbaijan, Moldova, and Czechoslovakia were part of the world's last, now deceased empire. Their breakup may turn out to be the old business of history, not the wave of the future. National self-assertiveness in the West can be mighty ugly, especially in its more extreme Irish and Basque versions. But when Scots, Quebecois, Catalans and Bretons talk separatism, they are, in the main, actually renegotiating their ties to London, Ottawa, Madrid and Paris.

They are the disputatious representatives of a larger, basically positive phenomenon: a devolution of power not only upward toward supranational bodies and outward toward common-wealths and common markets, but also downward toward freer, more autonomous units of administration that permit distinct societies to preserve their cultural identities and govern themselves as much as possible. That American buzzward empowerment--and the European one, subsidiary--is being defined locally, regionally and globally all at the same time.

Humanity has discovered, through much trial and horrendous error, that differences need not divide. Switzerland is made up of four nationalities crammed into an area considerably smaller than what used to be Yugoslavia. The air in the Alps is no more conducive to comity than the air in the Balkans. Switzerland has thrived, while Yugoslavia has failed because of what Kant realized 200 years ago: to be in peaceful league with one another, people--and peoples--must have the benefits of democracy.

The best mechanism for democracy, whether at the level of the multinational state or that of the planet as a whole, is not an all-powerful Leviathan or centralized superstate, but a federation, a union of separate states that allocate certain powers to a central government while retaining many others for themselves.

Federalism has already proved the most successful of all political experiments, and organizations like the World Federalist Association have for decades advocated it as the basis for global government. Federalism is largely an American invention. For all its troubles, including its own serious bout of secessionism 130 years ago and the persistence of various forms of tribalism today, the U.S. is still the best example of a multinational federal state. If that model does indeed work globally, it would be the logical extension of the Founding Fathers' wisdom, therefore a special source of pride for a world government's American constituents.

As for humanity as a whole, if federally united, we won't really be so very far from those much earlier ancestors, the ones huddled around that primeval fire beside the river; it's just that by then the whole world will be our valley.