WITH A cease-fire in place in Lebanon, the sorting-out of the latest Middle East crisis can begin. The very first item on the agenda must be Lebanon. For 10 years, and rarely more cruelly than in the last week, its neighbors have been crashing through its house. Now, with two of them (the Syrians and PLO) battered and the third (Israel) ascendant and prepared to bargain its new presence down, there may be an opening to assist the Lebanese to set their house right. Rehabilitation must go forward, and Lebanon's destiny must be returned to Lebanese hands. This means a government respectful of Israel's anti-terrorist interests but not an Israeli puppet.

Some confusing currents are running. In Washington, there is understanding of Israeli security requirements but a quiet shock verging on anger concerning the ferocity of Israel's attack, the evident expansion of its goals as the week wore on and the way it took advantage of President Reagan's distraction in Europe and of his initial tendency to indulge Israel on the basis of its claim simply to be securing its border. In other capitals there may be a mean resistance to the idea of reviving Lebanon on grounds that Israel will profit from it by gaining a good neighbor and some respite from terror, and that Syria and the PLO will lose in pride and strategic place. Still, no responsible government will allow its general feelings about the Mideast to get in the way of its specific obligations to Lebanon. That must be the priority.

No matter what unfolds in Lebanon, it is clear that Israel and the United States have reached a very troubled place. The difficulty is not merely that the Israelis, again, have embarrassed the United States in the eyes of friendly Arab regimes by the extravagant use of their military advantage. That is true, but honesty compels the offsetting admission that Israel was doing a nasty job that almost every other nation, including the United States, wanted done but did not have the heart to do itself. Most of the regimes in whose eyes the United States was embarrassed by Israel last week were scarcely embarrassed at all, as they should have been, by the years of Palestinian and Syrian abuse of prostrate Lebanon.

The real trouble lies elsewhere: in the disturbing impression the Lebanese affair has furthered in Washington that Israeli policy operates by a calculus of risks and options different from that of American policy and that it is constantly pressing at the limits of what most Americans think the American interest is. The sense grows that depending on circumstances, or perhaps on opportunities, there does not seem to be anything Israel might not undertake if it felt obliged or able to, regardless of how embarrassing or hurtful that might be to the United States. In the administration and elsewhere, along with the closeness to Israel there is the feeling that Israel makes heavy demands on American fidelity and repays it with a basic policy line that cuts across the American interest too much of the time.

In no way is this more evident than in relation to the Palestinian question, which casts the United States as the sponsor of an Israeli position that Arab peoples and governments everywhere equate --granted, often cynically--with injustice and humiliation. Egypt bet that by accommodating Israel's demands for security and acceptance it could get the Begin government to soften and come to terms with the concept of a Palestinian people. But Mr. Begin has not reacted this way. His repudiation of that concept has kept other Arabs from following Egypt to the table. Instead of recognizing their defiance as at least in part a response to his own rigidity, he depicts it as entirely a matter of hostility to Israel's right to exist. Israel's military philosophy follows.

President Reagan should subdue his pursuit of a chimerical "strategic consensus" and get serious about the American interests affected by the realArab--Israeli dispute. He should expect from Israel that it meet the Palestinians halfway: that it show readiness to find a way to live with them in mutual respect if they will do the same. The burden would then be on the Palestinians to match that offer formally and unequivocally. Even before the last week of war, Israel's aching loneliness and the Palestinians' tragic dispersion should have convinced them both of the wisdom of this course.