Imagine an even-handed student of the Middle East (on a sabbatical, perhaps, from a university on Mars) surveying the scene just days before the Israelis are supposed to pull out of the Sinai and the peace treaty with Egypt is due to come into full force. He or she (or it?) would have to be filled with despair and/or contempt with earthly ways.

What should be celebrated with joy and relief as the first great breakthrough toward peace in over 30 years of Arab-Israeli conflict is instead being approached with rancor, recrimination, rock- throwing, shootings and clubbings. Palestinians clash with Israeli occupation forces on the West Bank. Israeli troops tussle with Israeli extremists over the painful uprooting of the Jewish settlement at Yamit. The cease-fire across the Lebanese frontier with Israel remains on a hair-trigger hold.

The situation has rarely been so incendiary, the prospects for moving the peace process forward so remote. What happens next depends on the willingness of the principals to recognize the situation for what it is: a genuine crisis, in the sense that a small spark could ignite a large conflagration; but also a time of profound transition, crying out for an honest reappraisal of old risks and new opportunities.

This means that the United States, Israel, Egypt, and that disorganized amalgam of individuals, organizations and groupings that is so loosely called "the Palestinians" have got to give positive evidence of their acceptance of new as well as established realities.

What will be new after April 25, barring accident, is that Israel and Egypt will be formally at peace, with an international peacekeeping force on hand as guarantor. Israel cannot pretend that the end of hostilities with its largest adversary does not fundamentally redistribute the weight of the forces at play in the area. Surely, over time, this has to alter Israel's estimate of its own security--or insecurity--requirements.

But if Israel is obliged to reassess in the months ahead, the other parties are equally obliged to recognize that Israel's current fevered anxiety is real. Abandoning territory, dismantling a settlement, confronting massed PLO forces and Syrian SAMs in Lebanon--that's heavy stuff on top of Israel's chronic state of siege.

So if Egypt's President Hosni Mubarak is serious about his dedication to Camp David, he's got to stop "driving Begin almost crazy" (as one Israeli diplomat puts it) with loud demands for an independent Palestinian state--now. The same goes for the Israelis; they've got to stop pretending to keep the faith with Camp David while ruthlessly nailing down de facto annexation of the West Bank, proclaiming that territory forever Israel's.

The Camp David Accords are quite explicit: Nothing is to be foreclosed--the West Bank and Gaza are not to be forever anybody's-- until after a five-year trial of "full autonomy." And not even then, without mutual consent.

For its part, the Reagan administration can be excused for doing nothing more than "handholding" right now. But after April 25, only the United States can break the impasse. Plans are, in fact, under way; there's talk of resuming the stalled "autonomy" talks in Washington in late spring, with a flourish. But it will take the full attention of Ronald Reagan to give this process even a whisper of a chance.

Finally, those Israelis (and some Americans) who insist the next move is up to the "Palestinians" owe it to the interests of peace to define the term. "The Palestinians must take their fate into their own hands," says an Israeli spokesman. Does he mean the Palestine Liberation Organization, the only political instrument (however reprehensible its preachings and practices) that the stateless and governmentless "Palestinians" have at hand? If so, some way has to be found around Israel's absolute and America's conditional refusal to recognize the PLO.

Does he mean the supporters of the PLO on the West Bank (mayors and other notables) who have been harassed, repressed, cut off from each other by house or town arrest, or simply jailed? How do they give political voice to their grievances? Or does he mean the Israeli-organized Village Leagues, carefully culled from their Palestinian colleagues on the West Bank for their willingness to play ball with Israeli authorities? That's yet another sham. Deft diplomacy is going to be needed to bring some reasonably respectable representation of "the Palestinians" into the act.

Even an extra-terrestrial visitor would concede it's a tall order. But if it is the only reasonable way, it should not be beyond reach of mere Earthlings --the more so when you contemplate the alternatives.