No easy answers

What Americans, and allies in this hemisphere and abroad, most want to hear from President Reagan tonight is an honest appraisal of what the United States is up to in Lebanon and Grenada, the immediate crisis points in foreign policy. In what overarching pattern, if any, do they fit?

The public rating of Mr. Reagan's handling of foreign policy had been turning negative since summer. A month ago, well before the past weekend's traumatic events, a plurality of Americans for the first time since Reagan took office said they disapproved of his foreign policy performance.

To be fair about it, deepening ''unease'' better characterizes how the nation lately views the White House's foreign ventures than does ''disapproval.'' Opinion questions are not always answered literally. And the public's thinking sensibly reflects a foreign policy reality that is more mixed, a subtler compound of issues and interests than the art of questioning can describe.

What Americans most want is answers they can trust. ''Honesty and integrity'' were the two qualities that Americans, just last month, listed above all others in describing what they want of an ideal president, in a CBS/New York Times survey.

Next came expertise in handling foreign policy, caring about people, and qualities of intelligence and knowledge - notably ahead of handling the economy, domestic policy, and toughness. This was a telling response about the state of the nation the President will address in tonight's telecast.

The public is saying, We know there are trade-offs and risks, and at times you must act without full information. But given the experiences of Vietnam and Watergate, given America's history of exploitation in Central America and the violence and fixity of Middle East antagonism, we want to be sure about our government's motives. We are concerned our nation's energies and our servicemen's lives may be misspent.

The public and Congress are not about to ask President Reagan to renounce the balance-of-power role the United States has undertaken since World War II. The US cannot withdraw from the world and hunker down on this continent. Nor can it lash out when it suffers losses. What the practical-idealist American wants of his government is a judicious choosing of involvements abroad to find those his democracy can address.

This broader context and vision are what Americans worry about, more than hearing an explanation for the specific security failure at the Beirut airport, or for the specific threat to civilian life on Grenada, although these are important, too.

In making his larger case, Mr. Reagan should be cautious about reflexively invoking monolithic Marxism as the universal enemy - the Soviet-Syrian axis in the Middle East, the Soviet-Cuban danger in the Caribbean. Americans generally agree that the two systems - democratic and communist - are implacably opposed, on economic and political and religious grounds. But it is unconvincing to lump all communist systems together, just as it is to fail to discriminate among democracies. The Soviet, Chinese, and North Korean governments have competing systems and historic rivalries, as do ''free'' countries of the West.

Americans want reasonable talk and frank answers.

How long are we likely to stay in Lebanon? What is President Reagan doing to enlist Israeli and Syrian cooperation in Lebanon? What remains of his Middle East plan?

How long are we likely to remain as governors in Grenada? When the public there again votes for a new government, how sure is he that they will not again choose a socialist state? How comfortable is he, having just imposed the most powerful democracy's will on one of the weakest nations on earth, with the impact this will have on America's image abroad? The Reagan administration has spoken accusatorially about Soviet invasion, as in Afghanistan: How does the President differentiate his landing in Grenada from what the Soviets have done?

Remarkably, the central question of Mr. Reagan's tenure has shifted from his command of the economy and the revival of American power to unease about the wisdom and hard choices behind deploying that power. The public wants the reassurance not of easy answers, but of the candor and integrity that sometimes require the highest officials to acknowledge the dilemmas they face.