In reaching its judgment about the responsibility of Israeli Defense Minister Ariel Sharon for the Beirut massacres, the special commission understandably had nothing to say about Sharon's crucial role in the tactical decisions that brought the Israeli army to the gates of Beirut in the first place.

But his role is worth noting. As reliable informants reconstruct the decision-making, Prime Minister Menachem Begin was originally given two options by the military: a limited move into a 25-mile buffer zone in the south, or a sweep through the Bekaa Valley and on up north to Tripoli, leaving Beirut to one side. Sharon ultimately prevailed with a third option, which was to go for Beirut. It was a characteristic hammer- blow approach to the problem of how to ensure Israel's security.

This takes us to the one political implication of the commission's findings on which it seems safe to speculate. The decline, if not the fall, of Sharon as an Israeli political superpower seems almost certain. But if Sharon has been gravely discredited, the question remains: to what extent has "Sharonism"--a clearly defined and readily recognizable Israeli security doctrine--been equally discredited?

The answer could make a very big difference in Israeli policy--not to mention U.S.-Israeli relations--however the politics of the current crisis in the Israeli government eventually get sorted out.

As prime minister, Begin has been much more than nominally Sharon's boss: what Sharon did, it has to be assumed, Begin has supported, for whatever combination of policy/political reasons. But Sharon has been the professional military strategist--the driving, initiative force -- to whose judgment Begin more often than not deferred in the rough and tumble of Israel's Cabinet government.

Sharon has also been the most outspoken obstructionist of U.S. policy. He was openly contemptuous of both the follow-up Reagan "initiative" to Camp David and the efforts of U.S. special envoy Philip Habib to arrange the withdrawal of Israeli and other foreign forces from Lebanon. So it does not follow that things will be the same.

True, Begin needs, now more than ever, something positive to show for Lebanon. So a quick agreement on withdrawal is not in the cards. As much as ever, Begin is dedicated to a biblical view of Israel's claim to the West Bank, so progress on the larger Camp David "peace process" is not necessarily any closer. And Begin remains the most popular political leader in Israel.

But the weakening, one way or the other, of Sharon's freedom to run roughshod has to make some difference. For Sharon's view of the West Bank, just to begin with, has much less to do with religious history than it has to do with a grand geopolitical design. The same may be said of his support for the Israeli raid on the Baghdad reactor, the nailing down of Israel's hold on the Golan Heights, the big Israeli bombing raid on Beirut in 1981 and ultimately the Lebanese invasion.

So it is worth looking at a document in which, a little more than a year ago, Sharon laid out his view of "Israel's strategic problems in the 1980s." The document is actually a speech that Sharon never got around to delivering but made public anyway. He spoke of a radical Arab strategy "for the liquidation of Israel," predicating everything on open-ended Arab-Israeli confrontation "that presents an actual danger to our security."

So far, nothing special. Where Sharon goes further than anything said by any leading political figures is in his readiness to express explicitly the concept of preemptive military action (whenever and almost wherever) to meet potential threats. The Baghdad bombing was only a portent for Arab neighbors engaged in nuclear development. Lebanon was already a gleam in his eye: "We will prevent any violation of the status quo ante in Lebanon."

He would "prevent," as well, "the disruption of the territorial military status in neighboring countries"--suspicious troop movements or any "accumulation of forces in the confrontation area."

Sharon's central argument was that increased Arab capabilities (mobile armed forces and longer-range weapons systems) make Israel, with its occupied territory, no safer than it was behind its old borders before the 1967 war. On the contrary, "the lack of territorial depth" makes it necessary for Israel to dig in all the deeper on the West Bank, the Gaza Strip, the Golan Heights.

That is not a prescription for progress on Camp David's "full autonomy" for the occupied territories, with their ultimate fate left open to future negotiation. It argues for continued Israeli insistence on maintaining Israeli listening post and patrol rights within Lebanon even after a withdrawal agreement.

It is difficult to measure the degree to which "Sharonism" was uniquely Sharon. But "Sharonism" without the same old Sharon would lose much of its force. That's not saying much. But given the intractability of the current Mideast impasse across the board, it says something faintly promising.