THREE OF THE YEASTIER figures in American public life, Ronald Reagan, Daniel P. Moynihan and Henry Kissinger, have issued President Carter a vigorous, serious and politically weighty caution on his foreign policy. Speaking separately, they questioned in effect his contention, made at Notre Dame, that "we are now free of that inordinate fear of communism" of the past. Their warning, coming as Mr. Carter completes his shakedown, makes plain that his diplomacy will unfold under the same conditions of challenge and controversy that all his recent predecessors have known.

Gov. Reagan, speaking for conservatives, fears the Kremlin is not yet sufficiently reconciled to the status quo for the United States to indulge in heavy human-rights criticism of right-wing allies. Sen. Moynihan, adding the intellectual's refinement, worries that an attempt to enlist Moscow in world development may distract from "the reality of the military and ideological competition with the Soviet Union which continues and, if anything, escalates." Mr. Kissinger, still the strategist, warns of underestimating and thereby assisting the rise of Communists to power in Western Europe.

Are they, and those whose anxieties they articulate encumbered by an "inordinate fear of communism"? It is a strange question to ask of a country with a $100-plus billion dollar defense budget, in an administration run by an ex-submarine officer. That it can be asked at all indicates both the distance the United States has come from a single-minded preoccupation with the Cold War and the unavoidable confusions attending that move. The break with the past did not begin with Jimmy Carter, but it could hardly be expected that he could extend it by incipient acts (the Korean withdrawal plan, the opening to Cuba) as well as by attitude and rhetoric, without stirring doubts about his course.

We find ourselves broadly in sympathy with Mr. Carter's intent to add the "new global issues of justice, equity and human rights" to the "traditional issues of war and peace." He would adjust American policy to new imperatives of world politics and technology and domestic concern. He not only has an unfamiliar vision of the world. He has a palpable, almost startling confidence that it is in relative terms safe as well as right to seek out this brave new world.

At base, his serious critics contend that he lacks a sense of history, a sense of the menace of the dark forces that have dominated the century's politics. It is a formidable criticism and, of course, an unanswerable one, but it is incumbent on the President to address it, in idea and in detail, in order to have any chance to make his vision come true. If what we are witnessing is the renewal of a Great Debate on foreign policy, that's good news. A serious and responsible exchange of contrasting views and approaches would help rather than hinder Mr. Carter as he shapes and refines his policies and begins the hard business of putting them to work.