Jean Bethke Elshtain, the eminent University of Chicago scholar who died last month at age 72, was a little lady from a small town in Colorado who became a giant in the field of political philosophy. She gained her stature not by conforming to the orthodoxies of the modern academy, but by frequently offering compelling reasons to reject them.
In a milieu dominated by secularism, she embraced religious faith, in the end becoming a Catholic. Defying the radical feminism of the 1970s, she rejected abortion as the taking of innocent human life and defended marriage as normative for sexual conduct.
Of all her academic heresies, however, none was more upsetting to Elshtain's colleagues than her support for aggressive military action against terrorist organizations and, a decade ago, her defense of the war in Iraq. Having written about the politics and morality of war since the beginning of her career in the 1970s, Elshtain insisted that America's conflict with al Qaeda was not a matter of international law enforcement, as some insisted. It was a war.
Terrorists, and states that support them, are not merely engaged in criminal activities; they are our enemies—in the same way that Nazi Germany and imperial Japan were our enemies in World War II. As she wrote in her 2003 book, "Just War Against Terror: The Burden of American Power in a Violent World": "With our great power comes an even greater responsibility. One of our ongoing responsibilities is to respond to the cries of the aggrieved. Victims of genocide, for example, have a reasonable expectation that powerful nations devoted to human rights will attempt to stay the hand of the murderers."
That did not mean that force is always justified or that no rules apply. Elshtain was a believer in, and a leading interpreter of, the tradition known as "just war theory." This tradition does not propose pacifism—the view that the use of force is inherently unjustifiable. On the contrary, just-war theory says that in the face of unjust aggression, nations sometimes have a duty to use military force. They are also obligated to fight with all legitimate means to win—to defeat the enemy and halt its aggression.
Elshtain's view of war was fully in line with her general view of politics as a morally serious business. Any military action should be about advancing the common good and establishing principles of justice and human rights.
Because Jean was my friend and frequent collaborator, I have been asked more than once in recent days: What would Jean Elshtain have thought about Syria? Would she have supported President Obama's proposal to launch limited attacks to punish the Assad regime for its use of chemical weapons? Or would she have opposed the president's position—either because the administration has failed to make a solid case on just-war principles justifying military force, or because "pinprick" strikes to punish the regime without destroying it are too weak a response to its gross violations of human rights?
I do not know and would not presume to guess. But Elshtain would not have accepted the isolationist idea that the use of poison gas or other means to murder innocents is none of America's business. She recognized that a powerful and prosperous nation bears great moral responsibilities that transcend its borders.
For just-war theorists, that doesn't mean that U.S. is "the world's policeman." It also doesn't mean that military force is always the proper means for protecting human rights, or even that we are always justified in imposing by force what we regard, however rightly, as fundamental principles of justice. But it does mean that we should, working with other freedom-loving nations where possible, do what we can in a prudent manner to prevent mass murder by those George W. Bush accurately described, after the 9/11 terror attacks, as evil-doers.
Elshtain recognized, however—as have just-war theorists going back to St. Augustine through the modern popes—that even when force is used in a just cause there are additional requirements that must be met. Critically in the current debate, these include the likelihood of improving, and not worsening, the situation for the people of Syria and other potential victims of undeterred tyrants or violent extremists. Another concern is "proportionality"—the requirement that the collateral damage inevitably caused by the use of force not be so great as to render the use of force disproportionate and unfair to the innocent.
These judgments in any particular case will depend on careful empirical assessments of the facts. The sin, either way, is cynicism—defined here as the failure to treat politics, and war, as a morally serious business.
For Elshtain, Democrats and Republicans alike are obligated to lay aside political concerns about whether their votes will protect or harm the standing of President Obama. The lawmakers must deliberate the use of force on the merits. She would also be quick to note that the same moral duty falls on the president.
Mr. George, a professor of jurisprudence and director of the James Madison Program in American Ideals and Institutions at Princeton University, is a visiting professor at Harvard Law School.