IT IS a strange scene in the Mideast. Israel and Syria could go to war, in or over Lebanon, but the prevailing assumption is that any conflict would be contained, launched more to show steel than to alter the regional balance of power.The leadership in both Jerusalem and Damascus has engaged its prestige in a confrontation that seems accidental, even verging on unnecessary, to outside parties; but neither has geared up for full-scale combat. The United States and the Soviet Union have both dispatched ranking emissaries to the area, but, in Washington at least, there is little evident dispossition to lend reality to the resulting air of superpower showdown.

Not that some Israelis and some American hardliners are not calling upon the administration to accept the crisis as the first Soviet-inspired test of Ronald Reagan's will. They see Syria, a Soviet client, flexing its muscle in Lebanon and moving into a new position that challenges Israel's previous command of the skies and support of the Christians, and they demand that Mr. Reagan respond in a way showing the stuff he is made of.

It could come to that, but so far, to Mr. Reagan's credit, it has not. He has implicity accepted that there is more to the crisis then a Soviet-Syrian probe of his mettle. There is, for instance, some Christian elbowing in Lebanon and some pre-election pulling and hauling in Israel. Mr. Reagan got Mr. Begin, the Israeli prime minister, to put off attacking the new Syrian missile position in Lebanon. He summoned rumpled and reliable Philip Habib out of retirememt and sent him to try to turn the clock back a month or two.

This is well. The longtime design of Syria's President Assad, as of his predecessors, appears to be the tuck Lebanon into a "Greater Syria" -- a development that Israel would be justified in regarding as strategically disadvantegeous. At the same time, the instinct Prime Minister Begin is to strengthen Israel's connection to Lebanese Christians, in order to keep Syrians and Palestinians on edge, and this is a development that Syria is justified in regarding as to its strategic disadvantage.

To frame the problem this way is to suggest the solution: a neutral Lebanon. It is necessarily a long-term goal, but all outsider diplomacy must be measured by how well it succeeds in loosing Syria's and Israel's grip on a country whose soveignty both have flouted shamelessly. "At the end of the day," a Beirut diplomat told James MacManus of The Manchester Guardian, "no one gives a damn about Lebanon except Syria, for historical reasons, and Israel, for security reasons." That's not exactly so. Lebanese give a damn. But others have gotten in the habit of denying them the right to sort out thier own painful affairs.