There is among economists a sort of missing generation, between the giants of the 1960s and the whippersnappers of today. The Samuelsons, Friedmans, Galbraiths, Steins and others who became brand names then are in their seventies or even eighties today. The new generation of bright kids, who look on 51-year-old Martin Feldstein of Harvard as a kind of uncle, are for the most part in their thirties.

In between are many distinguished economists: Joseph Stiglitz, Mancur Olson, Amartya Sen, Gary Becker, George Ackerlof, Elhanan Helpman and Robert Lucas, to name a few. But relatively few of this in-between generation have the kind of involvement with a single issue or a point of view, fought out in the popular press, that makes an icon, much less a household word. Harry Johnson is one, but he's dead; Jagdish Bhagwati is another, very much alive -- as is Lester Thurow. Both are partisans on different sides of the single issue that is most likely to divide the economists' house in the 1990s: the question of free trade.

Johnson, of course, was a peripatetic Chicagoan -- the operating arm of George Stigler and Milton Friedman, a close student of the world trading system, a dauntless foe of protectionism. As an unflagging commuter to Europe, he sometimes wrote two papers on a single transatlantic flight. When he died in 1977, of a stroke at age 53, it was said that he had so many publications in the pipeline that most economists didn't know he was dead for three years. Pragmatic, monetarist, lucid, skeptical, tart-tongued, but above all, free trade: That was Harry Johnson. Next week his pupil, Bhagwati, will turn up in London to honor him with a lecture on the current threats to the General Agreement on Tariffs and Trade and free trade generally. There is no economist better known on trade today -- or better able to defend it -- than Bhagwati.

Surely it's an auspicious time to pop with a defense of what is sometimes derided as the ''general agreement to talk and talk.'' With heads of state and finance ministers of the Group of Seven leading industrial nations meeting in Houston this week, it is subsidies to farmers -- and how to fairly ratchet them down -- that is the leading issue on the table. But there is much more to it than that. The rules for trade in services, for the preservation of intellectual property rights and for the tendency of the world to break itself up in trading blocs will be discussed in Houston, too. All these controversies must be resolved to some degree, then tabled, by the end of the three-year Uruguay Round of negotiations in December. But since the spring, the GATT talks have been at an impasse and gloom about the future of free trade is growing. It was Thurow who said, at a symposium in Switzerland as long ago as 1988: ''GATT is dead.''

Can it be? After the Bank for International Settlements, surely the least-well-understood of the major international coordinating agencies. Staffed by only a hundred or so career civil servants in Geneva, GATT has eight times since World War II convened the stately paced talks known as ''rounds.'' Mainly through a commitment to playing by the rules, these negotiations have all but eliminated the tariffs and other barriers that for a couple of centuries had plagued the trading nations; 97 nations have joined the organization, including 10 since 1982. China is negotiating and the Soviet Union is next in line. But with crass taxes banished, attention in recent years has shifted to the wide range of ''non-tariff barriers'' by which nations are said to be able to close themselves to key foreign goods. A stereotype of the ''predatory'' Japanese of the 1980s and 1990s has replaced the image of the ''ugly'' Americans of the 1950s and 1960s. Legislatures and newspapers are full of proposals to bring the other fellow into line.

The threats to GATT come from four different directions, Bhagwati says. First, there is the the rise of the perception of unfair trade practices, he says. It was aggravated by the wide range of protectionist measures instituted in the wake of the second oil shock and amplified by the effects of flexible exchange rates. One important source of it is what he calls America's ''diminished giant syndrome'' -- the profound nostalgia (from which Great Britain suffered in its day) for the period in which America utterly dominated a ruined, war-torn world.

Then there is the issue of ''managed trade'' -- the conviction in some quarters that high-technology industries are so important they cannot be left to the marketplace. Non-economists are standing in line to manage America's industrial policy, Bhagwati notes; many economists, whom he thinks should know better, are sharpening their pencils to prove that a philosopher-queen, with nearly perfect information, could in theory outfox all her trading partners -- in theory, at least.

Meanwhile, an aggressive and unattractive unilateralism is also breaking out, especially in the United States, where the Super 301 section of the 1988 Trade Act permits Congress to play trade cop to the world -- in direct contravention to the multilateral spirit of GATT. ''As 301 and Super 301 actions are undertaken, unilaterally accusing others of unfair trade practices and demanding their removal, the notion is also reinforced that others are unfair traders, creating a poisoned atmosphere which conventional protectionists can hope to exploit to their advantage,'' Bhagwati writes.

Finally, a new emphasis on regionalism may be subtly threatening to the spirit of GATT. A North America free-trade area, Pacific free-trade area and the European Common Market are now all the rage. The liberalization of the communist regimes will surely accelerate the trend. But these regional free-trade compacts aren't antithetical to GATT unless they're used that way, as a kind of straw man with which to beat up on the over-arching plan, Bhagwati says. ''

Which way out? Well, one notion now gathering steam is a Canadian proposal for a World Trade Organization, a much higher level of visibility for GATT with beefed-up responsibilities and powers. Fine in due course, Bhagwati says, but at the moment it is overreaching -- a ''grandiose task'' that threatens the success of current negotiations. The trick is to let GATT continue to slowly evolve into an organization capable of undertaking still more ambitious tasks -- not to try to kick it up to whole new levels of complexity all at once.

The controversy over GATT's future is not likely to light up the sky -- at least not unless it deteriorates into a series of escalating skirmishes. But a powerful coterie of analysts exists that would prefer to replace the Cold War with the almost equally threatening specter of a trade war. Bhagwati's broadside is a powerful argument for ''trade management'' arrayed against a large group of advocates who feel they must ''manage trade.''

David Warsh is a columnist for the Boston Globe.