The world's hope and belief that a new year will bring peace to the Middle East may be premature. President Anwar Sadat's dramatic initiative the sensation of 1977, is the great question mark of 1978.

"Everything has changed . . . the world after the Jerusalem visit is completely different from the world before the visit," declared Sadat, with Prime Minister Menahem Begin sitting at his side, at the conclusion of the Ismailia conference last weekend. Yet, the inability of these two men to agree on an approach to the Palestinian problem, a failure that takes on more of the appearance of deadlock with every passing day, belies Sadat's sweeping conclusion.

Much has changed with stunning swiftness in the Arab-Israeli dispute, but much also remains unchanged. To understand what is happenind and why a rescue mission by President Carter may be essential to revive the flagging momentum, it is necessary to distinguish between what is new and what is unaffected.

The sights and sounds of change in my just-completed trip to Egypt, Israel and Jordan - my fourth visit to the region in 21 months and the first since Sadat traveled to Jerusalem - left impressions that are unforgettable.

Imagine riding across the desert between Cairo and the Suez Canal in a police-escorted Egyptian bus alongside an Israeli journalist wearing a patterned yarmulke on his head and carrying a book in Hebrew. Or sitting across the desk from a Cairo office worker, who is pouring coffee and saying, "We have been wanting peace for 30 years. Today Israel is a fact and there is no way around it." Or sitting at a table for four late one night near the Pyramids outside Cairo, drinking bottles of Omar Khayyam Egyptian wine with an Israeli editor, an Egyptian diplomat and a West German correspondent, and solving the troubles of the world.

Egyptian and Israeli delegates to the Cairo conference joined American officials in rousing choruses of "O Little Town of Bethlehem" and other Christmas carols around the piano at the American ambassador's house. An Egyptian waiter on a yacht plying the Nile displayed scars on his body from three wars - 1956, 1967 and 1973 - and an Israeli journalist aboard unveiled a scar from the fourth war between them, 1948. A Cairo cab driver refused payment when he discovered that his passenger was from Israel - until the visitor produced and signed a small Israeli bill as souvenir, and the cab driver kissed it as a sign of friendship.

Thanks to television diplomacy, which unleashed pent-up yearnings for better lives, people are ahead of their governments. Sadat's daring unexpected and highly symbolic journey to Jerusalem - transmitted instantly via modern electronics to the homes and public places of Israel, Egypt, the Arab world and across the seas - had a mind-changing power that not even the main actors anticipated.

"I never knew that it (the trip) would have such repercussions all over the world and among my people also," the Egyptian president told Time Magazine in a "Man of the Year? interview. He and other diplomats poorly understood that saturation "as-it-is-happening" television coverage of a compelling event can have unprecedented impact on those who watch and listen.

From the time of the Pharaohs until the age of communications satellites, man did not have the ability to hurl fragments of experience across borders and oceans. This is ssomething new, something that altered the Middle Eastern problem within an hour after Sadat alighted from his plane to shake the hand and troop the line of the waiting Isaeli leadership.

The principal effects of Sadat's act and the interplay that followed, as best they can be seen today are these:

First, Egypt has been taken out of the anti-Israeli military front for several years at least and possibly much longer, no matter what happens on the diplomatic front. The Egyptians have found voice for a growing belief that the quarrel with Israel, and the heavy military costs thereof, present crushing and unnecessary burdens.

Egypt needs peace and knows it, and it has been able to express this freely. It sees itself today as Egyptian first and pan-Arab second. An effort by Sadat or a successor leadership to reverse field toward support for another war would be difficult in the short run, unless Egypt were physically attacked.

U.S. intelligence has estimated that it would take at least 18 months before the run-down Egyptian military forces would be in position to hurt the Israelis in an attack. And this does not reckon with the political difficulties within and outside the army, especially if Egyptians saw themselves as being asked again to fight and sacrifice for an Arab cause not wholly their own.

Second, Sadat's political recognition of Israel has had great impact and cannot easily be taken back. Israeli leaders have appeared side by side with Arab leaders, shattering the 30-year-old of diplomatic isolation and setting the precedent for direct negotiations.

"This is no longer a conflict between Arabs and a state whose existence they do not accept," observed Shlomo Avineri the professor and diplomatic thinker who served recently as director general of the Israeli Foreign Ministry. "Now it is a conflict of entities with difficulties between them but which are in direct contact."

The dramatic, de facto recognition by the largest Arab state has deeply affected Israeli thinking. According to Prof. Louis Guttman, scientific director of the respected Israel Institute of Applied Social Research, the Sadat visit ranks with the 1967 and 1973 wars in its effect on public opinion. Guttman reported that close to 90 per cent of Israeli Jews responding to his most recent polls believe Egypt is now interested in real peace with Israel - up sharply from the 40-to-60 per cent holding this view in the past. This shift in opinion is what has made Begin's decision to return the Sinai to Egypt almost costless politically.

Third, Sadat has made a powerful breakthrough for the Arabs in public opinion elsewhere, especially in the United States and Europe. U.S. polls indicating a public belief that Egypt is more interested in peace than Israel may shift back in time, but the credibility of Sadat and other moderate Arabs has made a giant leap. If and when he needs it in his own cause, "Superstar" Sadat can obtain a world-wide hearing which no other Arab leader - and few national leaders outside the United States - have ever been accorded.

Having said all this, it is necessary to examine what has not changed in the weeks since Sadat's initiative, or what has not changed very much. These factors are at the heart of the present difficulty.

First, the Israeli official position on the Palestinians in the occupied West Bank has remained unacceptable to Sadat and the other Arabs. The Begi government submitted a proposal for civil "self-rule" but has not agreed to military withdrawal from this area or to self-determination for the resident Palestinians.

Begin has said flatly that Israeli troops will not withdraw in the short run and held out no promise that they will ever do so. A key figure in Begin's government said privately of the West Bank. "We won't give it up." This is not acceptable to Sadat or to Jordan's King Hussein, a key figure in any West Bank bargain, nor is it acceptable to West Bank residents on the terms they have been offered.

Despite Sadat's powerful effect on Israeli thinking about all things Egyptians, thinking about all the overwhelming public consensus against a general return to Israel's 1967 borders and against creation of a Palestinian mini-state remains unchanged. Nonetheless, according to Prof. Guttman there has been no consensus either before of after Sadat's visit regarding the future of the West Bank (provided that no independent state is created there). This division of opinion provides Begin an opening to find a West Bank compromise that Arabs and Israelis alike could accept - but there is yet no indication he intends to do so.

Second, Sadat's solo initiatives, sprung suddenly on his fellow Arab statesmen, infuriated more rejectionist or radical Arab states and offended such relative moderates as Jordan's King Hussein and the Saudi Arabian leadership.

Syria's President Hafez Assad, convinced that Sadat will obtain nothing for the Pan-Arab cause from Israel despite the legitimacy that he has given has vowed never to cooperate again with the Egyptian leader. Moreover, Assad has begun planning a new military buildup to strengthen his position against Israel, in recent days asking the Soviet Union for new weapons and reportedly sending a new military mission to Moscow.

Just as Sadat's go-it-alone policy has shattered the potential Arab unity for war, so it has shattered the fragile Arab unity for peace. For the time being the Arab confrontation states and Palestinian representatives are unlikely to restore the common front and working relationship needed to negotiate the comprehensive settlement with Israel that everyone professes to seek.

Finally, there is the anger of the Soviet Union, left out of the Egyptian-Israeli negotiations and repeatedly goaded by Sadat. The Soviets cannot bring about a Middle East peace but they can pose serious obstacles through arms supplies and other support to Syria, the Palestine Liberation Organization and others. The change from a U.S. Soviet agreement on objectives in October to Soviet exclusion today carries the seeds of danger.

Begin's West Bank proposals and particularly his hard line presentation of them to the Knesset on Wednesday sent shock waves through the Arab world, being taken by many there as proof of the rejectionist claim that Israel will never face the Palestinian issue. "The immediate reaction here was, 'That's the end of Sadat,'" said a Jordanian official who believes that the Egyptian's credibility will be soon destroyed unless the promise of an acceptable Palestinian solution can be resurrected.

Perhaps only President Carter, who devoted so much time, effort and political capital to the Middle East during his first year in office, could make much of a dent on some of the difficult problems that remain. Given their nature, it will not be easy even for him, whether on a flying trip or through quieter diplomacy.

After the rapidly shifting currents and cross-currents of 1977 in the Middle East - Carter's determined drive for a comprehensive settlement, the unexpected election of Begin, the frustration of Carter's drive and the hold decisions of Sadat - anyone seeking to forecast the immediate future would be foolhardly or worse.

Public opinion and political belief can change quickly, as we have seen, and they can veer again in response to new events. All ideas are reversible over time. As 1978 begins, however, the peoples of Egypt and Israel and a good many others inside and beyond the Middle East are hoping for peace with an intensity unmatched in the past three decades.

I saw the eagerness on the faces of the Egyptians waving to Israeli officials and journalists in the overcrowded streets of Cairo and the country lanes near the Suez Canal. I felt it both in Israel and Jordan, and no more so than on my way between them over the narrow Allenby Bridge across the River Jordan. A man named Isaac was my cab driver from Jerusalem through Jericho to the bridge, and a man named Mohammed met me on the other side to drive me to Amman. Each has seen and suffered through four wars, and each in his own way is praying for peace.