JAMES BAKER last week called the mess in Iraq "the first post-postwar crisis," meaning of course that, Panama notwithstanding, it was the first major confrontation of its kind in decades that would not be played out under the familiar rules of U.S.-Soviet gamesmanship. That would make George Bush's speech last Wednesday, in which he justified his commitment of U.S. military power to Saudi Arabia, our first post-postwar rhetorical flourish.

No small event. Indeed, Bush's opening words seemed self-consciously to herald a new epoch. "In the life of a nation," he said, "we're called upon to define who we are and what we believe."

That call has had a certain enhanced urgency since communism limped off-stage last year, leaving us holding a bag of Cold War assumptions in which we had invested much of America's postwar politics and culture. Because heads of state never draw more heavily on national mythology than when they are dispatching soldiers to risk their lives, Bush's address stood to be an important indication of the role for which America's political culture would begin preparing in the post-communist world.

It was in fact a revealing address, one that suggested that, for purposes of identity-making, there is little of our traditional mythology to draw on these days, and that implied potentially larger cultural problems ahead.

Bush cited two reasons for committing military force to Saudi Arabia: that "we must resist aggression," a moral imperative; and that the United States "could face a major threat to its economic independence," making military commitment a practical necessity. So far, so good. In the political language we have spoken and heard throughout our history, our moral and practical incentives to action have always been presented as separate and distinct. We have not always openly acknowledged any practical interests we may have had in a given conflict, but we have consistently defined our military actions in terms of a higher historical purpose. We have, at various times, used our military strength to realize our manifest destiny, to make the world safe for democracy, to build an arsenal of democracy against fascism and to halt the spread of communism. The last time we committed troops to the Middle East, for example, Ronald Reagan pointedly explained that the Marines were in Lebanon, among other reasons, lest the region "fall into the hands of a power or powers hostile to the free world . . . .

It doesn't matter whether such a rhetoric of higher purpose reflected a national consensus or sought to create one. It doesn't even matter whether any of our various higher, moral purposes actually existed. This is the way great powers do business: by telling themselves they are fulfilling their responsibilities to history.

In his Wednesday address, George Bush was unable to continue in this tradition. The vocabulary that had served so many of his predecessors was simply not available to him. We heard a post-communist political language forming in his speech, a language in which the moral and the practical reasons for action become the same reason. In the current crisis, the aggression we are resisting is directed not against an ideal for which we stand, but against our wallets.

Bush tried hard to stake out a historical responsibility that the United States could fulfill in the Saudi desert. Saying that "America has never wavered when her purpose is driven by principle," Bush several times invoked the traditional American battlecry of "freedom." He tied our Saudi commitment to the "struggle for freedom in Europe" in terms of continuing Western "stalwartness," and noted generically that "we must resist aggression, or it will destroy our freedoms."

But Bush's only effort to link Kuwait or Saudi Arabia to freedom was to note the West's heavy dependence on Persian Gulf oil and to declare that Saudi independence is thus in our "vital interest." The role of the threatened Gulf states in the machinery of freedom remained, in the logic of Bush's address, purely economic.

Bush's major rhetorical device, in constructing his argument against aggression, was Hitler, whom he evoked by a reference to "blitzkrieg," by delicately noting "the case in the 1930s" (apparently so that he would not have to say the word, "Germany") and by recalling the lessons of appeasement. In demonizing Iraq's Saddam Hussein, an eminently demonizable figure, Bush was able to draw on a vital aspect of American culture: hatred of the bully. Saddam Hussein's sudden media Hitlerization was already well underway by the time Bush spoke, another chapter in a process we have seen several times in recent years involving such figures as "strongman" Noriega of Panama, the "fanatical" Khomeini of Iran and Libya's "madman" Gadhafi. But if Bush set out in his speech "to define who we are and what we believe" in the post-postwar world, then the portrait he has drawn suggests some serious cultural challenges ahead of us, at least in the absence of yet more dramatic changes in the world. Bully-hatred offers obvious cultural satisfactions, but no one has ever built a national identity on it. The world is full of bullies, and some of them are our friends. The ones Bush suggests deserve to be put in their place are those who directly threaten our interests. Those interests seem to be devolving to what's in our billfolds.

Great powers protecting their material interests is of course the way the world has always worked. When we prop up the weak Middle Eastern regimes that are economically important to us, to cite a single historical parallel, it is not much different from the way in which the British propped up a tottering Ottoman Empire for decades in the 19th century: A stable Middle East served their material interests.

But the rhetoric of higher historical purpose, so clearly missing from Bush's speech, is not a luxury. The ability to influence events in one's interests comes at great cost to a culture, not only because maintaining an effective military has become fantastically expensive but because citizens will sometimes be called upon to risk their own lives. They need to believe it's worth the potential sacrifice, and simple material wealth has not often been used to persuade them. Among the reasons is that those serving in a nation's armies are rarely the same people who enjoy that nation's riches. Few people will be willing to die for somebody else's ability to heat a bigger house than they'll ever live in, or to drive a fancier car.

Great powers thrive on fulfilling their perceived historical missions. They have at various times carried out their historic "mission to civilize," or borne the "white man's burden," or spread the "true faith" among the "heathen," or assisted history in creating the "dictatorship of the proletariat." When the consensus belief in that purpose has been shattered, as happened to us in Vietnam and apparently to the Soviets in Afghanistan, great powers have found their power difficult to wield.

"Standing up for our principle is an American tradition," Bush said Wednesday. He's right. But now what?

Charles Paul Freund is an Outlook editor.