They laugh as the Israelis and the Egyptians sit down this week with the Americans to resume negotiations on the hard part of the Camp David "framework for peace"--the "autonomy" talks on a form of self-rule for the Palestinian Arabs on the West Bank and in the Gaza Strip.

By "they" I mean the Europeans (who have their own political and commercial fish to fry in the Middle East), the hard-line Arabs like Syria and Iran, the so-called moderate Saudis and Jordanians, and assorted critics in this country as well. Menachem Begin won't bend, they say. Anwar Sadat doesn't really care. The Arabs who matter won't be there.

Camp David is dead. Abandon hope.

They may be right. But Camp David has been pronounced dead, and hope abandoned, so many times that a second opinion is advised. It begins with the tumultuous history of the Arab-Israeli conflict. What that says is that stalemate--the absence of any forward movement--can lead quickly to violent and explosive movement backward.

"Peace is a process," as Henry Kissinger was fond of saying, and almost everybody agrees that for better or worse, Camp David is the only process showing signs of life. So the mere existence of continuing "autonomy" talks provides a crucial safety valve. Better yet, the negotiating format can be re- shaped, expanded, modified. Still better, it is not foreordained that, even in their present form, the talks will necessarily fail-- though that case can certainly be made.

Begin's obstructionist settlement policy, the Israeli security clampdowns on the West Bank, the land and water grabs--all this, it is argued, is fast closing the door to "autonomy." Sadat, some say, is interested only in the second part of the "framework," the concurrent Camp David negotiations that would return to Egypt the last Israeli- occupied slice of the Sinai. With that in hand, Sadat's support for the Palestinian cause would be perfunctory.

The Reagan administration, the argument runs on, is so transfixed with strategic consensus-building against the Soviets that it has no sense of the inextricable connection between progress on the Palestinian issue and any prospect of a collective Israeli-Egyptian-Saudi Arabian effort to counter the Communist threat. Witness the easy ride given Begin on the "autonomy" issue on his visit here.

And finally, of course, there is no prospect now that the West Bank Palestinian Arabs, whose participation in any "autonomy" plan is crucial, will have any direct hand in shaping it.

That is a formidable array of downbeat arguments, the more so when you consider the seemingly irreconcilable difference in the fundamental objectives on both sides: annexation is Begin's "ideological commitment," an Israeli official is frank to concede; Sadat's is an independent Palestinian state.

Which brings us nicely to the upbeat argument. It begins with Camp David's artful, open-ended ambiguity. While its West Bank "autonomy" approach guarantees nothing final, it also forecloses nothing--not annexation, or independence, or federation with Jordan or Israel, or some new kind of entity.

Rather, it temporizes by offering a five-year trial period of limited self- rule, with talks to resume within three years on what comes next. Five years is a long time for hard lines to soften, antipathies to dissipate, and longer-term approaches to emerge. It is longer than Begin (or perhaps Sadat) may be in control.

The big questions remain: whether either has sufficient incentive to start down the "autonomy" road; and whether, even if Israel, Egypt and the United States can somehow manage to run some mutually acceptable "autonomy" plan up the flagpole, anybody would salute.

For Begin, one big incentive is pride of authorship. The "autonomy" idea, he claims, was exclusively his. For both him and Sadat, there is pride of place in history as co-architects, with Jimmy Carter, of Camp David, warts and all.

But there are practical incentives, too. Sadat needs progress on the Palestine question to avoid, with the return of the Sinai, the appearance of a self- serving "separate peace." Begin needs, for the loss of the Sinai, what Israelis call "real peace." Only the full range of relations with Egypt (political, cultural, trade, and all the rest) can sustain a claim to have settled relations with Israel's most formidable adversary. "Real peace" is Sadat's to bestow.

So there is leverage on both sides, and the late April 1982 deadline for the final Sinai withdrawal becomes a target for completing "autonomy" negotiations as well.

Would the Palestinians collaborate --and at what stage? All I would argue is that the reality--or the imminent prospect--of an "autonomy" agreement, however inadequate to Arab hard-liners, might be harder for practical West Bank Arabs to boycott or dismiss than an unspecific promise with no details filled in.

Wishful thinking, perhaps. But doing something, almost anything, creates its own momentum when the alternative of doing nothing is so dangerous.