Liberty! Equality! Fraternity! For generations of democratic revolutionaries, those three words have been both a battle cry and an elusive ideal. In this country, we currently have no shortage of vigorous advocates for either liberty -- especially for protection of economic and property rights of the individual -- or for equality -- with decidedly different proponents pushing their case for a more even distribution of our aggregate goods and honors. But what was missing all through last fall's campaign, and has not been sighted since, is a national voice to advocate the value, let alone the cause, of fraternity -- the shared commitment that transforms us from a mostly prosperous assortment of private individuals into a nation of public citizens.

The Republicans are the champions of liberty, the Democrats of equality. But on the virtue of fraternity, both parties fall mute. Pollster-analyst Daniel Yankelovich tells of encountering "a growing hunger for community and commitment." But the political parties obviously don't believe it, ignoring any call upon our time and appeal to our sacrifice for the common good. They must believe we are self-centered and mean-spirited.

And dumb, too. That's the only plausible explanation for the ritualistic bickering between congressional representatives of the two parties in what is supposed to be, but isn't, a continuing debate over national defense. The Republicans seem never to have met a weapon they didn't like, and they love to keep buying new ones, although they stoutly resist raising money to pay for them. Democrats, by contrast, publicly yearn for a defense that is "leaner, cleaner and cheaper," but in fact they seem opposed to any new weapons, and then wonder why American voters harbor serious doubts abot their grasp of the dangers loose in the world.

But all of that publicized bickering, with all the spontaneity of professional wrestling, has nothing to do with what our responsibility as public citizens is or ought to be to each other and to our nation. What about our national "resolve" and "will"? Was George Washington wrong when he argued that the privilege of being an American justifies a duty to serve the nation? And could it be that American resolve and will are not as firm, as muscular as those of Sweden and France, to cite just two national communities that have concluded that the privilege of citizenship imposes a duty to defend the nation by serving in the armed forces?

You might think the Democrats, because of their commitment to equality, would feel obliged to oppose a national policy that largely exempts from the responsibility to serve in the nation's defense forces those who can qualify and afford to go to college. ut Democrats seem to find nothing wrong with America's relying on marketplace incentives to meet its defense personnel needs. And of course Republicans have no argument with a system that enables young men from good (Republican) neighborhoods of Pacific Palisades and Scarsdale to avoid the wrenching personal experience of living for months in the same barracks with their social inferiors from places such as Cleveland and Newark.

National defense is only one aspect of fraternity. But it's time to give some thought to determining what it is in 1985 that constitutes public citizenship and what it asks of all of us private individuals.