'A people without walls is a people without any choice." So writes Aristotle in The Politics. In modern parlance, we might say that a nation that does not adequately defend or define its borders subjects its citizens not only to military risk but to political danger. A country that cannot maintain its deterrent capability vis-a-vis its hostile neighbors rapidly loses strategic maneuverability, becomes enervated and finds itself increasingly helpless. Israel, as recent events have once again made lamentably plain, risks becoming such a country. Fifteen Israelis were wounded Wednesday - four seriously - by a Grad-model rocket that hit a shopping center in Ashkelon just hours after US President George W. Bush arrived to celebrate the state's 60th anniversary. Southern District Police chief Cmdr. Uri Bar-Lev said the rocket, fired from Beit Lahiya, had been made in Iran. The attack on Ashkelon, a city of 120,000, came two days after 69-year-old Shuli Katz of Moshav Yesha was killed by a Kassam rocket. Her death followed the killing of Jimmy Kedoshim last Friday as he did his weekend gardening in Kibbutz Kfar Aza. One is hard-pressed to think of another country that would tolerate such a relentless barrage. What would America or Britain do if, heaven forbid, explosives were launched at Paramus, New Jersey's Park mall, or at London's Brent Cross shopping center? THE CURRENT Israeli policy - to absorb damage and casualties, try to strike at rocket launchers and gunmen in Gaza and periodically declare, as Prime Minister Ehud Olmert did on Wednesday, that the assaults are "entirely intolerable"- is no longer viable. Military Intelligence chief Amos Yadlin warns that Hamas has several dozen rockets capable of striking targets within a 20-kilometer radius, and that within two years every community within a 40-kilometer range, including Beersheba, is expected to come within range. Nor is negotiating a cease-fire with Hamas, tempting though this may seem, likely to prove a viable strategy. First, because of the nature of the enemy. It bears recalling that Hamas supports the establishment of an Islamist Palestinian state over all of Mandatory Palestine. The destruction of Israel is its raison d'etre. Second, as Hamas leader Khaled Mashaal has himself declared, the organization would do its utmost to use a temporary truce to rearm and regroup. Third, negotiations on a cease-fire would serve to strengthen Hamas and weaken the Palestinian Authority led by President Mahmoud Abbas. Finally, the combination of faltering negotiations with Abbas and cease-fire negotiations with Hamas would likely reinforce the Palestinians' impression that only the radical Hamas movement can achieve results in the "struggle" with Israel. That's why Vice Premier Haim Ramon was right when he declared on Thursday: "We have to put an end to the Hamas government." ISRAEL HAS no claims on Gaza, having wrenched out its civilians and withdrawn its military in 2005. But since the Hamas government there has chosen to pursue violence across the border, relentlessly targeting Israel's civilians - including those who supply the people of Gaza with fuel and electricity - Israel's necessary course of action is clear: to begin restoring deterrence along the Gaza border. This requires a series of escalating steps beginning with the elimination of Hamas's key leaders, and continuing with relentless artillery fire at the sources of rocket launches, while making every effort to minimize civilian casualties. Ultimately, so long as the danger persists, "putting an end to the Hamas government" may necessitate temporarily retaking some or even all of the Strip. All this must be accompanied by public diplomacy, stressing that Israel has no long-term interest in occupying Gaza, and that such action in defense of sovereign Israel's citizenry is legitimate under international law. As Stephen Schwebel, who served as president of the International Court of Justice in the Hague, said, "A state acting in lawful exercise of its right of self-defense may seize and occupy foreign territory as long as such seizure and occupation are necessary to its self-defense." Eventually, Gaza could be returned to Abbas's control, which could then be bolstered by European and Arab League forces. Perhaps then the rehabilitation of Gaza could finally begin. Experience has long since shown that Israeli vulnerability and indecisiveness invite aggression. Only by restoring deterrence and securing defensible borders - which mandates the uprooting of Hamastan - will Israel be able to protect its citizens and work toward peace and a genuine two-state solution.