An excess of caution, and of thinking along lines outmoded by the events of the past month, make it seem that a chintzy Israel offer threatens peace prospects with Egypt. In fact, Prime Minister Menahen Begin is bringing relatively generous terms to President Anwar Sadat.

My strong, impression, after having seen both leaders recently, is that the Israeli proposals are more far-reaching than originally intended by Begin or expected by Sadat. While an accord is not certain, it will take a major-league banana peel to cause events to slip off the path to settlemtn.

The starting point for analysis is the offer itself. While it has not been made public, the leaks - presumably by Israeli hard-liners hoping to shoot down the offer - leave little doubt about the proposals.

The first feature of the offer involves the Sinai desert and the Gaza Strip - territories under Egyptian rule that Israel occupied in the Six Day War of 1967 and only partially returned in the disengagement accords of 1974 and 1975. The Israelis now proposed complete return to the 1967 frontiers. They are not asking, as they once did, for military presence at strategic spots.

They seek only to maintain settlement in certain sensitive areas - notably Rafi near the Gaza Strip and Sharm al-Sheikh, which gives Israel access from the Gulf of Aqaba to the Red Sea and the oceans of the world. But those settlements would clearly be under Egyptian sovereignty.

By itself the principle of return to the 1967 frontiers in Sinai implies a major concession across the board. It will be very difficult for Israel to offer less than return to the 1967 lines on the Golan Heights, if Syria, from which that territory was taken in 1967, decides to enter the negotiations. Neither will it be easy - and this point is cardinal - to recede from the principle of total return in the lands on the West Bank of the Jordan River.

On the contrary, the offer now being made by Begin on the West bank territories prefigures their eventual abandonment by Israel. Begin proposes self-rule, or autonomy, for the Palestinian Arabs living on the West Bank. There will also be some kind of Israel security presence, presumably along the Jordan River.

But self-rule means that the local population will have the eventual right to choose its sovereign ruler. Anybody who doubts that point should consider this exchange between Marvin Kalb and Begin on CBS's "Face the Nation" last Sunday:

Kalb : Does self-rule also mean self-determination?

Begin : I think one can say so, synonymous they are.

I do not see how President Sadat can possibly afford to refuse so generous an offer. It makes it possible for him to go right to work on negotiating return of Egyptian territory to Egypt. It gives him an offer that he can relay to the Palestinians and King Hussein of Jordan for eventual Israeli abandonment of the West Bank. It also gives him the makings of an offer he can relay to President Assad of Syria anytime the Syrian leader wants to join the game.

In other words, Sadat's fondest hope - the hope of managing a settlement for the whole Arab world - is brought alive by the offer Begin outlined last weekend in Washington. Knowing the Israeli prime minister a little, moreover, I assume that the offer he actually brings to Sadat will be at least a little sweeter than the one he has been talking.

To be sure, things can still go wrong. The Russians, the Syrians and the more radical elements of the Palestine Liberation Organization have a strong interest in knocking the Israeli offer and making Egypt refuse it. Some Americans - particularly officials who specialize in the Syrians, the PLO and the expectation of Israeli intransigence - are going to be disparaging the offer as not good enough.

Fortunately, President Carter is not playing it that way at all. In dealing with Begin and Sadat in the last few days, at least, he has been at once supportive and unobtrusive. The statement put out by the White House last Saturday night after the Begin-Carter meetings was exactly what the doctors ordered. It emphasized the President's "appreciation" of the prime minister's constructive approach . . . understanding and statemanship."