Responsibility for the outrage was claimed by the Islamic State, although officials have identified a cell of militants with various allegiances, including the local Salafist extremist group Ansar al Shariah. The Arab world is reeling from an unprecedented wave of Islamic extremism, in part financed by sympathizers in oil-rich Persian Gulf states and unfortunately exacerbated by America’s “war on terror.” The West must now decide whether the young Tunisian democracy is worth saving. 

From Iraq to Libya, and Syria to Yemen, the status of democracy in the region is a catastrophe. Even Egypt has reverted to its authoritarian ways. Today, those in the region who have survived the mayhem yearn for a more stable Middle East, for a chance to find their way and fulfill the destinies of their peoples.

Bold action, by the United States in particular, could make a significant difference. If the West perceives Tunisia as a new light in the otherwise dark Arab political sphere, it might help the country stand up to extremist assaults. But if it chooses merely to pay lip service to Tunisia’s achievements, the risk is that the newly elected government may fail. The consequences of this choice are grave.

The Obama administration and the United States Congress have an opportunity to amend future historians’ judgments of America’s misguided interventions in the Middle East by coming to the aid of the one success story of the period. And Tunisia’s political achievements are all the more important because they are not the product of American armed intervention. 

The country’s secular democracy owes much to cultural factors: the peaceful character of its people, their middle-class culture, respect for women’s equality, regard for education, moderate practice of Islam and social tolerance. Unfortunately for the hopes of many at the outset of the Arab Spring, these preconditions for democracy simply did not exist in the rest of the Arab world.

In January 2014, just three years after Mohamed Bouazizi immolated himself — an act that incited the Tunisian revolution, ending 23 years of dictatorship — the transitional assembly adopted the new Constitution. Islamists held a majority of seats until the elections last fall. But the secular opposition successfully resisted the push of the Islamist party, Ennahda, toward theocracy and Shariah law. Tunisia’s recent presidential elections were universally applauded for their transparency, fairness and civility. In January of this year, President Beji Caid Essebsi pledged to respect and defend the new secular Constitution.

The Islamist terrorists who struck weeks later at the Bardo Museum could not accept or even fathom such a bright future. Tunisia’s success as a democracy is incompatible with their perverse, absolutist, almost nihilistic interpretation of Islam. They will not cease until Tunisia declares its allegiance to an archaic form of Islam incompatible with Enlightenment principles — what my Sorbonne professor, the French philosopher Paul Ricoeur, called the “hermeneutics of suspicion,” the interpretive power of critical reason applied to our beliefs and our texts.

How can the United States come to Tunisia’s assistance in its hour of need? President Obama’s recent phone call to Mr. Essebsi was appreciated, but words of sympathy are surely far less than the moment requires. To convey a stronger message, America’s president should schedule an early visit to the country, address its newly elected Parliament and let Tunisians know that they are, from now on, among the strategic allies of the United States on the basis of shared democratic values and interests.

Congress should, for its part, promptly issue an invitation to Mr. Essebsi to address a joint session of the legislature upon his first official visit to the United States. Congress should also offer a far more significant package of economic, military and financial assistance than the present $61 million appropriation for Tunisia, particularly since the country’s tourism industry, which accounts for about 15 percent of the country’s economy, will certainly be affected by the museum attack.

Tunisia only recently emerged from four years of financial mismanagement by the Ennahda-led transitional government. A donor conference, including other major Western countries, would provide the setting for an effective response to Tunisia’s economic needs. Tunisia needs more than symbolic gestures to combat Salafist terrorists determined to cripple the Tunisian economy by frightening off Western tourists and investors. 

Tunisia’s security sector is also vulnerable and in need of support, including more modern military equipment and intelligence-gathering tools. The government has to contend not only with a 300-mile border with a chaotic, post-Qaddafi Libya (a huge arms bazaar for Islamist terrorists of all stripes), but also with as many as 500 returning Islamic State fighters who must be prevented from launching further attacks like the one at the Bardo Museum. Effective exchange of information between the American intelligence community and the Tunisian security apparatus should be mandated by Congress.

Cooperation on security should extend to NATO countries, too. It is clear that Islamic State-inspired jihadists are aiming at Europe no less than at Tunisia, with the Mediterranean region serving as shelter for a new breed of terrorists who can easily disappear among the local populations. It is estimated that about 2,500 susceptible, misinformed Tunisians are fighting in the ranks of the Islamic State. They, too, might one day return and spread havoc. 

Why wait for another Bardo tragedy to deal with this threat? There is as much at stake for the West in the attack at Tunis last week as there was at Paris in January: It is the same fight.

March 27, 2015 (Published in The New York Times. Republished following the author's permission).