THE world longs for continuity. But it fears the apparent change that is one of continuity's conditions. And it undervalues the mental effort needed to succeed.In the Middle East, the Bush administration has demonstrated political courage in bringing to Madrid the parties in the dispute over Israeli-occupied land. Events assisted: Political change in the Soviet Union, desperation there for economic links to the West, and an Iraq war that left the United States with singular diplomatic authority as well as broad United Nations support, have created an opportunity for a peace settlement between Israel and its neighbors. The slogan "land for peace" has to be refin ed: How much land for how much peace? Which land? Israel will not likely give up the hills that command the approach to Jerusalem. What political authority, how fast for the Palestinians? The American Secretary of State James Baker has his hands so full with the Madrid talks that he can hardly take notice of the fighting in Yugoslavia. And yet if events there continue to deteriorate, the White House could have this too dropped into its lap. One proposal to President Bush: Order a US naval fleet into the Adriatic as a message to the warring parties to "cool it." In both cases the Bush administration would have to make a practical calculation as to the effectiveness of action, after deciding whether there were some moral or historical imperative for getting involved. The view here is that the United States does have a world role. Its moral responsibility should at least equal its economic and military strength. It should have a leadership agenda that it should constantly be enlisting its colleague nations to support. Joseph G. Harrison, a longtime Monitor correspondent, foreign editor, and managing editor, wanted this newspaper to publish repeatedly, on its front page, the agenda of world problems that most needed attention. No easy ones for Joe: He would have included the Yugoslavia breakup, the Madrid talks, and social issues like education for those slipping behind. Harrison, a decade and a half into retirement, passed on the other day at his Cape Cod home. We had just talked before I headed to Europe. He was as f ully informed about world events as ever. Harrison was the fastest and strongest writer I have known among hundreds of colleagues at this paper. A lead editorial could take him 20 minutes to write. He was a specialist in the Indo-European languages. He wrote simply, in Anglo-Saxon rather than Latinate prose; he would not let you escape his meaning. He could be tough on those who could not defend their positions; he wrote tenderly on behalf of children. But here it is his relentlessness in facing the demands of world leadership that is emphasized. We should all become more aware of the continuing effect and presence of right arguments. They do not quit. It is easy to get discouraged. How many times have the world's leaders tried to broker peace in the Middle East? Jimmy Carter helped arrange the accord between Israel and Egypt: Egypt's Sadat was assassinated; Israel's Begin settled into a profound privacy; and Carter, thanked, still lost the White House. And yet the Camp David achievement continues. Yugoslavia had all the privileges of the West while its Central European counterparts languished, and it is the first to come apart under old hatreds. A good negotiator shows why change - "concessions are necessary to assure the kind of continuity the antagonists want. The kind of continuity we all want, the assurance that our individual being - whether as persons or as peoples - still carries forward despite the apparent loss of property, despite change within family circumstances or cultural units as we have known them, takes mental effort to maintain. Our patience may have to develop new dimensions, our sense of time take on more of the immediacy of eternity. At the least we ought to incline toward support of world leaders who give their idealism a try. If humanly speaking they are not exceptional people (although they often are), their responsibilities are exceptional. These supportive citizen efforts help create a mental climate where the continuity of progress is rescued from old circumstances and cynicism.