Ronald Reagan's Middle East address did more than offer hope for a "fresh start" in that troubled part of the world. It marked a fresh turn for his presidency.

Not that his proposal contains all wisdom. Of course it does not. Nor that it guarantees success. No one initiative, no matter how carefully crafted, can break with a single stroke the historic impasse between Arabs and Jews there. But it was a creative, promising step nonetheless.

Perhaps more important, and welcome, it signaled the emergence of a different President Reagan.

In the 20 months he has been in office, much has been made about his public personality (pleasing, naturally) and his actor's skills. They have enabled him to become, it is widely said, (again, the Great Cliche) "the Great Communicator." Yet his has been essentially a passive, if not negative presidency. It has been one that seeks to turn back the clock, to undo past actions, to hold the line. With his Mideast speech, Reagan moved into a more active role.

He seized the right moment to act, and he was firm and statesmanlike in enunciating U.S. policy. The opportunity for peace was there, he was saying, and he fully intends to see that the United States exerts its best efforts to help achieve it. It was his most impressive performance as a world leader. In the best sense of the word, he was presidential.

Obviously difficulties lie ahead, as the immediate, predictable reaction to his proposal indicates. But by acting swiftly, clearly and decisively he has put pressure on all parties to join in real action to begin, as he said, to "lay the groundwork for a broader peace in the region." Now the world will see just how seriously, and responsibly, the respective sides respond to this American initiative over the long term.

Of all the problems, none looms larger than that of what happens to the territory on the West Bank of the Jordan River. The heart of that question involves Israel's continued determination to keep building "settlements" there among the overwhelmingly Arab population. These are not temporary outposts, constructed for strategic reasons. They are permanent fixtures intended to create a fait accompli. By making the West Bank in reality a province of Israel, they make moot any negotiations over that area.

As Ariel Sharon has said, with typical bluntness, about Israel's intention to keep adding settlements on the West Bank: "We will leave an entirely different map which no one will be able to ignore."

This sort of intransigence is difficult enough. Compounding it is the assertion that Israel has an inalienable right to do what it wishes in that territory, the Arabs and the rest of the world notwithstanding.

Lest there be any doubt about that right, Menachem Begin is quick to cite the ultimate authority. It's right there in the Bible. Read the first Book of Genesis, the one that lays out how it all began with the darkness and the void and the light and the firmament and the rest, and you will come to Chapter 17, Verse 8. There are quoted the following words spoken by God almighty to Abraham. And I will give unto thee, and to thy seed after thee, the land wherein thou art a stranger, all the land of Canaan, for an everlasting possession; and I will be their God.

What God gave Abraham, and thus the children of Israel, became part of the ancient land of the Jews, Judea and Samaria, or today's West Bank.

With that sort of authority, how can there be any further discussion of the subject? Yet, would you believe it, the message of the God of Abraham gets translated a bit differently among Arabs.

In his book, "Israel Now: Portrait of a Troubled Land," Lawrence Meyer offers an examination of the entire West Bank question that is especially timely. Particularly useful is his discussion of the impact on Israel of Begin's unyielding West Bank policies.

"No other policy of the Israeli government is as potentially subversive of the original Zionist ideals, as expressed by Herzl, Weizmann and Ben-Gurion, as is the continued occupation of the West Bank and Gaza," he writes. "No other policy threatens to undermine Israeli democracy or to deflect the energies of Israel in the way that a continuation of the occupation does. As a domestic political issue within Israel, the continued occupation is clearly one of the most explosive confronting the body politic. Quite apart from the damage that Israel's continued occupation of the West Bank has done to its international position is the cost that Israel has had to pay in compromised principles and values. More than that, the Israeli occupation reopens the long-dormant question of rights over territory, a debate long thought to be settled."

Meyer goes on to say:

"Almost any argument that Israel can make in claiming all of Palestine can be made by Palestinian Arabs as well. Both Jews and Arabs can point to a period in the distant past when they were sovereign in Palestine. Both have centuries-old ties to the land. For both, Jerusalem has religious significance. Both have populations that were rendered rootless by their dispersion from the land.

" . . . The one claim that Israel can make that the Arabs cannot, that the land was promised by divine covenant, is the one claim that carries the least weight among non-Jews. As an arguing point, Israelis pressing the Jewish claim to the West Bank suggest that if Jews have no claim to Hebron or Nablus -- the two principal population centers on the West Bank -- then they have no claim to Tel Aviv or Haifa. It is an argument that Arabs are only too happy to accept, since Arabs deny the Jewish claim to any of what they still call Palestine. In pressing their claim to all of the ancient Land of Israel, Begin and his supporters reopened the old question of whether Jews have a rightful claim to any of it."

Which is only another reason to hope that Reagan's Mideast proposals will be taken by Israelis and Arabs alike as a serious opportunity to make a fresh start. It is in all their best interests.

Lighter, holiday note, or back to baseball again:

If you think the big-bucks-and-all-for-me state of mind that characterizes today's professional sports has expunged the emotion and loyalty from the hearts of fans, savor this one. A fan, responding to last week's column about Rickey Henderson and others tearing up old Ty Cobb's records, writes, in spidery longhand:

"Just in case you are a little too 'smug' about breaking all of Cobb's records, the ones that really make him the greatest ball player of all time are (1) leading the league 11 or l2 times in batting and (2) a lifetime batting average of .367, buddy.

"Try that one on for size."

The letter was signed, "Old Timer."

Got it, Old Timer, and it fits.