"A VERY GREAT achievement . . . a return visit . . . we are resolved not to have any more wars . . . we agree that Palestinian Arabs should be represented at Geneva . . . we will continue the dialogue . . . the key word is continuation . . . we shall have President Carter with us in the next phase."

If you believe there is any hope for some break-through to end the 30-year conflict in the Middle East, what more could you have expected Israeli Prime Minister Menahem Begin to say in his interview last night with CBS's Walter Cronkite, and with Egypt's President Anwar Sadat at his side? Nothing more, in our view, despite the inclination of Mr. Cronkite and others to look for "agreements" and to worry about "a let down" and "deflated" expectations. As Mr. Sadat said, "People will try to picture the whole thing as deflated." But our sense of it is that the extraordinary coming together of the president of Egypt and the prime minister of Israel in Jerusalem, at the Knesset and in their private talks, measurably inflates the prospect of real progress toward a Middle East settlement. They have agreed, both men indicated, on a way to proceed, which will include the other Arab states and American diplomacy as well. And that is as much as could be expected.

The speeches in the Knesset earlier in the day could not have been anything other than starting points for the bargaining to come. They did not offer even the promise of a settlement or a peace treaty. But, uttered as they were in the context of the new psychology created by the Sadat visit, they marked the beginning of a deeper and more promising negotiating process.

Mr. Sadat, offering Israel acceptance in the region, made the standard Arab demand for a return of all territory lost in 1967 and declared this matter nonnegotiable. In interestingly general terms, he also called for Palestinian self-determination. Mr. Begin declared in response that "everything" was negotiable and appealed for direct negotiations with Israel's other Arab neighbors and with "legitimate spokesmen" of Palestinian Arabs. And, unilaterally, he declared open Israel's Egyptian border. Each leader projected a dignity and a sense of history and, perhaps most important, a respect for the other's political circumstances befitting the uniqueness of the occasion.

It makes no sense to hold the two speeches up to the light, so to speak, looking for detailed points of agreement or disagreement as though on the texts themselves falls the burden of establishing whether the mission "succeeded" or "failed." The texts are only indicative. Their significance lies less in content than in context: They are messages exchanged by two men, who, we believe, are genuinely determined to exploit this unexpected turn in their region's tormented history. They are the words of two men who realize that, having gone this far, they can go back only at an unbearable cost to the welfare of their nations and the common peace.

It is not by one visit, or even a reciprocal Begin visit, that the results of this new era will unfold. It is by the slow cumulative growth of a mutual respect and trust - growth that can make possible steps and formulas scarcely conceivable before. We are as curious as anyone to see what the next step will be. By what actual process will this initiative be sustained? Assuming the Israelis can give real momentum to negotiations, will the opposition to Mr. Sadat in the Arab world deter him from continuing his quest? And so on. It is foolish to expect the answers all at once and now. The answers will come, if they come at all, only as time ripens the relationship newly begun in Jerusalem.