Before the world has another anti-Israel field day over the death of seven members of a Palestinian family on a Gaza beach last Friday, it might (though of course it won’t) reflect on the two cases of Mohammed el-Durra and Jenin. In both, you may recall, Israel was lynched by the world media for atrocities it never committed without a chance to defend itself, and in both the truth had little power to rectify the damage when it finally came to light.

This time, too, it is far from clear that Israel is responsible for the deaths of the seven Palestinians. A preliminary investigation has indicated that there were apparently no Israeli shells or missiles fired at Gaza at the time the beach explosion took place. Perhaps it will yet turn out that there were. For the moment, though, anybody with an open mind on the matter would be advised to keep it open.

But even if an Israeli weapon did kill the seven, Israel has nothing to apologize for. While the deaths were awful, they were accidental. No one on the Israeli side intended them. No one on the Israeli side wanted them. This is, of course, not something that can be said of the many hundreds of homemade Palestinian rockets that have fallen on Israel since the disengagement from Gaza nearly a year ago. Of these, every single one has been intended to kill or maim as many Israelis as possible. Their failure to do so has been a result only of their primitiveness, not of the restraint with which they were fired.

On a purely public relations level, this has been a problem faced by Israel throughout its conflict with the Palestinians. Although the Palestinian armed organizations have sought to cause the deaths of a maximum of non-combatant Israelis, they have been relatively inefficient in terms of the effort they have expended. But although Israel has sought to harm a minimum of non-combatant Palestinians, its far more destructive weaponry has caused deaths even when no attempt was made to cause them.

A Palestinian stone thrown at the head of an Israeli soldier is meant to kill but rarely does. A rubber bullet fired by an Israeli soldier at a Palestinian stone thrower is not meant to kill but occasionally can. In the court of world public opinion, this is the disadvantage of being the militarily stronger party.

But the situation is grimmer than this. Until now, Israel has made a real and generally successful effort not to kill Palestinian non-combatants. It may not be able to keep this up much longer.

It comes down to a matter of deterrence.

So far, despite all the counter-measures it has taken, Israel has been unable to deter Palestinian rocket attacks from Gaza. While it has been able to destroy some of the rocket-producing workshops, to wipe out some of the rocket-firing teams, to keep others of them from deploying by creating fire-free zones they don’t dare venture into, and to kill some of their commanders, the rockets themselves have kept coming. Intolerable for the residents of a town near the Gaza Strip like Sderot, which has had to put up with almost daily barrages, they have been tolerable for the country as a whole only because their short range and inaccuracy have rendered them extremely ineffective.

Yet it is just a matter of time before the Palestinians manufacture or smuggle into Gaza longer-range rockets – and when they do and will be able to hit not just small towns like Sderot, but southern cities like Ashkelon and Ashdod, and eventually perhaps even Tel Aviv, accuracy will no longer be a factor. When firing into urban areas, one can nearly always be sure of hitting something even if it is not what one aimed for – even if one aims, for that matter, at nothing special at all.

At this point the arithmetic will change. When Palestinian rockets begin, not to wound one Israeli every time 30 of them fall, but to kill 30 Israelis when one of them falls, Israel will have no choice but to up the ante. And this it will have to do by means of massive artillery and air strikes that will take a heavy toll of innocent lives.

This is the simple logic of warfare. You win by punishing the enemy more than the enemy can punish you. As long as he is killing or wounding only a few of your citizens, you can respond by killing and wounding only a few of his – and by trying to limit this to guilty parties. If he is killing and wounding many, you have to kill and wound more, and guilt or innocence can no longer be a factor. And this, although it has refrained from doing it so far, is something that Israel has the means and power to do.

Moreover, the rocket attacks from Gaza must be stopped, not just because they are unacceptable in themselves, and not just because they are liable to become worse, but because, as long as they continue, Ehud Olmert’s government can forget about trying to implement the second stage of disengagement in the West Bank that has been its political banner. If withdrawing from most of the West Bank, which is within easy range of Jerusalem and major population centers in Israel’s coastal plain, means a rain of rockets on such places as well, there is no way the Israeli public is going to buy it.

It’s ugly to say it and ugly to think it, but if in the end these attacks can only be stopped by killing more Palestinians than the Palestinian people can bear to have killed, thus forcing them to pressure their leaders into putting an end to them, that’s what will have to happen. Let’s hope it doesn’t come to that.

Mr. Halkin is a contributing editor of The New York Sun.