There are signs that the general initial shock at the casualties caused by the Israeli invasion of Lebanon is easing or at least blurring as time passes and the initial PLO-inspired body counts are questioned. Public concern, following the lead of official concern, seems to be shifting from the human costs of the operation to the political possibilities opened by it.

In one sense, this cannot happen soon enough to suit the Israelis. They have smarted under humanitarian censure. They consider the criticism political in effect if not in intent, since it could limit the extent of support they can expect to receive in this country for their purposes in Lebanon and elsewhere.

In another sense, however, the censure is extremely useful to the Israeli government. It validates an image of savagery and uncontrollability that constitutes that government's most powerful leverage in its attempt to pry the PLO completely out of Beirut and Lebanon. This is not what critics of Israeli policy have in mind when they take to the ramparts, but it is, involuntarily and ironically, one of their effects.

David Ignatius of The Wall Street Journal neatly summarized the other day the delicacy of Israel's dilemma in West Beirut: to appear belligerent enough to frighten the Palestinians but not so belligerent as to alienate critics at home or in the United States.

The American policy dilemma follows accordingly: to appear concerned enough over casualties to not appear to be giving Israel free rein but not so concerned that the PLO gets a free ride.

It is, I think, an awareness of this dilemma that in the six weeks of the Lebanon operation has shrunk the circle of those raising an open cry about casualties to genuine humanitarians and enuine propagandists. They are not always easy to distinguish from each other.

In many other people, there is disappointment, naive perhaps and somewhat hypocritical but nonetheless real, to find that a seemingly civilized fellow Western people could act as the Israelis have in Lebanon. But it appears to be more of a residue, which is serious in its own right and will not be forgotten, than an emotion propelling political action now.

Like a lot of others, I am somewhat ambivalent about this result. Certainly no cry is too loud to draw adequate sympathy to the civilians who have been chewed up by the Israeli military machine. Never mind that Israelis are far from the only offenders in Lebanon and that the PLO defined the battlefield by its deployments.

Those who have spoken for the victims --even in emotional and exaggerated terms, for that matter even in calculating and propagandistic terms--need make no apologies to those who have made alibis for the perpetrators. Anyone who has shielded his dismay about the death and suffering out of doubt about the provable numbers or out of an inclination not to be "unfair" to the Israelis or not to embarrass them has had his priorities badly out of whack.

I feel nonetheless that the casualties and the new refugees are only a part of the story and not the dominant part. This is a cold position, since, by extension, it lets the Israelis get away with some awful things and amounts to a retroactive endorsement of their operation. Some people, stuck on the casualties, simply gag on it.

But it is the only position that lets one deal with the new reality created by the invasion and that gives one some chance to ensure that those casualties were not incurred in vain. To me, it makes no sense to hold that the invasion was so intrinisically flawed that it is impermissible to seek benefits from it.

This is the logic of the more unforgiving critics, conspicuously the secretary of defense, Caspar Weinberger. He has denounced the invasion, denied it any justification either before the fact or after the fact, and called for the Israelis simply to retire behind their own borders. He evokes the American interest in improving ties with moderate Arab states--which themselves do not take a position as extreme as his.

The more sensible position, it seems to me, is to find a place in the overall deliberations for the human aspect of the crisis, but to keep the political aspect in the center