By all appearances, George P. Shultz has produced a victory for quiet diplomacy during his maiden voyage through Western Europe as secretary of state.

What remains to be seen after his 13-day journey through seven allied capitals ended yesterday is the durability of gains that Shultz clearly seems to have achieved.

Those gains were in restoring a measure of trust to American leadership, polishing the Reagan administration's badly tarnished image in Europe, achieving somewhat better unity within the Atlantic Alliance and, perhaps most importantly, defusing sharp disputes literally over bread, butter and ideology that threatened to tear apart the alliance.

The former corporate executive, business school dean and Treasury secretary showed himself able to apply his penchant for quiet problem-solving to foreign policy in this trip through West Germany, Belgium, the Netherlands, Italy, France, Spain and Britain.

Just one month ago, U.S. relations with France were severely strained. The French, who treasure their independence in all matters, deeply resented the White House's implication that France had made concessions in its attitude toward trade with Moscow to induce the United States to lift sanctions imposed on suppliers to the Soviet natural-gas pipeline project.

Yet last week, Shultz and French Foreign Minister Claude Cheysson sat together, formally attired, sipping brandies, calling each other by their first names and explaining to reporters how they had agreed on new studies of trade with Moscow.

Just one month ago, the prospect of an agricultural trade war loomed between an increasingly angry United States and most of Western Europe's heavily subsidized producers.

Yet, 11 days ago in Brussels, Agriculture Secretary John R. Block told reporters that there would be somewhat of a truce while a group was established to study the problem more thoroughly.

Sitting next to Block was Shultz, a calm and pleasant man who does not ruffle easily and who, in private sessions with quarreling U.S. and European officials, had cooled the rhetoric and set up the study group.

The key word is "studies"--the business school approach, and that of Shultz.

The real test will come this spring when the study results are known. Only then will there be a clearer picture about whether allied willingness to compromise is real or disputes have merely been postponed.

In his five months as secretary, as in much of his career, Shultz has been known as a highly intelligent and effective conciliator, a management expert and economist who believes in talking things over and working things out.

If the study groups fail to produce compromise, Shultz the conciliator may become Shultz the fighter and arm-twister.

A somewhat related situation could develop with Spain's new Socialist government of Felipe Gonzales.

Shultz, who celebrated his 62nd birthday during the trip, and Gonzalez, 40, got along very well during a Madrid meeting, observers for both sides reported. The visit was deemed important because Gonzales, during his election campaign, promised to review and submit to public vote his predecessors' decision to join the North Atlantic Treaty Organization.

The United States wants Spain to stay in the alliance, and the Spanish government--certainly its military -- is probably inclined to remain. Public opinion, however, seems to be against membership.

Shultz came to assure Gonzalez that the United States wants to deal with all elected democracies, even Socialist ones, and to put the young leader at ease.

But some Spanish observers believe it may be a year or two before Gonzalez is strong enough politically to try steering Spain into staying in NATO, if that is what he favors. Some allied officials believe that NATO will not tolerate that wait, forcing Shultz to exert pressure sooner rather than later.

The picture of Shultz as a pragmatist, an executor of Ronald Reagan's foreign policy instincts with no wide-ranging strategic concepts of his own in foreign policy (with the possible exception of the Middle East) seems accurate, but it is hard to tell for sure from the outside.

Although Shultz spent much time with reporters accompanying him, he revealed very little about himself or his ideas. He prefers little or no public discussion of issues by officials until internal government decisions are made.

He does not seek publicity, makes as little news as possible and seems to prefer it that way. "The last thing he wants," one official said, "is to have something known as 'the Shultz Doctrine' of foreign policy."

His performance is in sharp contrast to that of his predecessor, Alexander M. Haig Jr. One U.S. diplomat summed up the feeling of many: "It's nice to have someone calm again."

While Haig and Shultz share similar views about the importance of Europe and the need for understanding its interests in Washington, Shultz appears to have a more positive effect on allied leaders. Some of this is due simply to the fact that after several years of sometimes bitter quarreling with Europe by several U.S. administrations, both sides seem anxious to settle down.

French President Francois Mitterrand, according to French officials, is said to have told colleagues that his meeting with Shultz was the best he has had in many years with a top U.S. official.

Shultz clearly benefits from his close relationship to Reagan. Europeans say they have far more confidence in what Shultz tells them because they always feared that Haig would be sabotaged by White House aides.

Most importantly, Shultz was welcomed in London because he is viewed as having skillfully persuaded the White House to lift the pipeline sanctions, widely perceived as ill-considered.

Shultz's favorable reputation abroad is also due to his style and presence. While he seems so low-key to reporters that it is frequently not clear how he feels about something, authority seems to flow naturally to him.

"In six months, Mr. Shultz has made a major mark upon the world . . . . And he has certainly put his stamp on United States foreign policy," British Foreign Secretary Francis Pym said Saturday in a remark echoed generally in all capitals.

If Shultz is putting his own stamp on foreign policy, it may well be in boosting the link between international economics and diplomacy to new heights. He lights up when discussing economics, and he talks about it often with all foreign leaders.

Most importantly, they want to talk about it, especially with the international economic recession influencing so many foreign and defense policy decisions.

Like many Europeans, Shultz tends to measure security questions with a large dose of economic data rather than exclusively in terms of military power.

He is very committed to free trade and greatly concerned about the collapsing global economy, believing that most of the world's problems have economic roots. This, in his view, inhibits problem-solving, reinforces protectionism and ultimately keeps making problems worse.

His concentration on economics combines with a view that Europe, as an economic superpower, is central to U.S. interests and security.

In simple terms, his aides say, he believes that, if the West improves its economies, it will first help itself, improving cohesion within the alliance, making defense more affordable and reducing pressure to sell goods to Moscow at cut rates that could strengthen the Soviets.

It will also, he believes, eventually rejuvenate Third World markets, removing major instability the Soviets can exploit.

Shultz seems comfortable echoing Reagan's basic instincts about the Soviet threat. But he does not believe that economic pressure will humble Moscow, his associates say, and tried to reach out cautiously throughout this trip with a message that the United States is prepared to respond positively to improving relations if the Soviets reciprocate.

Also apparent after the trip, however, is that even as confident a man as Shultz cannot be perceived as probing Soviet attitudes without worrying about ultra-conservatives in Congress and the White House.

He complained about stories from the NATO meeting in Brussels that portrayed the alliance communique as generally more "conciliatory" in tone toward improving relations with Moscow than previous communiques. He also quickly issued a statement contradicting a wire-service dispatch edited to suggest that Shultz was "softening" his tone toward Moscow.

"Softening" was probably not the correct description, but the official party was concerned in both cases more with the impact on readers in official Washington than in Moscow.

Shultz went to Europe to extinguish some fires and to try developing a more cohesive allied policy toward the Soviets at a time of new leadership in Yuri V. Andropov. He also sought to bolster morale and unity so the alliance survives 1983.

Cheysson has said next year will present the most serious challenge to the alliance since the end of World War II because of the continuing recession and scheduled European deployment of the new U.S. nuclear-tipped Pershing II and cruise missiles.