In the last decade, the United States has launched three military interventions (in Kosovo, Afghanistan, and Iraq), and the decade to come may bring even more such actions. As of this writing, Iran continues its clandestine efforts to build a nuclear weapon, and North Korea has tested (with limited success) a long-range missile. Should the U.S. attack Iran or North Korea preemptively? If so, when and how? These are probably the most difficult questions an American president in the next decade will have to face. And so there is cause to welcome Harvard law professor Alan Dershowitz’s well-timed Preemption: A Knife that Cuts Both Ways.

Dershowitz, whose eminence in the law is nearly as great as his celebrity, has never been able to resist throwing himself into the issues of the day. He has written books on Israel, Bush v. Gore, the Bible, abortion, and the O.J. Simpson and Claus von Bulow cases. But scholars who wander outside their specialty do so at their own risk, and Preemption is a case in point.

The book is noteworthy for taking a series of positions: Dershowitz believes Israel was within its rights to launch a preemptive attack in the Six-Day War, to attack Iraq’s Osirak nuclear reactor in 1981, and to selectively target (or assassinate) terrorists. He opposed the war in Iraq (though he says it was “a 51-49 percent matter, with the deciding 2 percent based on the law of unintended consequences”). And in the case of Iran’s nuclear program, he appears to believe that the United States and Israel have the moral and legal right “to protect their civilians and soldiers from a threatened nuclear holocaust, and that right must include—if that is the only realistic option—preemptive military action.” But he expresses doubts about an attack that would cause “undue civilian casualties and other costs.”

Dershowitz is entitled to his opinions, but whether they are persuasive is another matter. Unfortunately, Preemption provides no theory or framework for thinking about the issue of preemption. Dershowitz appears to be oddly rudderless. He correctly observes, as foreign policy and international relations specialists have for a long time, that there is a difference between preemption (using force in anticipation of an imminent enemy attack) and prevention (attacking before an enemy poses a threat). He complains that there is no coherent jurisprudence on the use of preemptive or preventive force, and certainly none that nations appear to follow. He is right on that score, too.

Dershowitz offers a long list of factors that he believes should be considered in deciding whether to carry out a preemptive attack, including the type of military action, reasonable alternatives, effect on civilians, reliability of intelligence, and the certainty, severity, and immediacy of the enemy’s potential attack. But he provides no method for balancing any of these elements against each other. He likes the philosopher Kant (who would have opposed preemption), but he also likes Bentham (who would have supported preemption). “In eclectic, heterogenous democracies,” Dershowitz writes, “no jurisprudence will ever reflect a single ideology or worldview. Nor should it. It should incorporate Benthamite utilitarian principles that weigh costs against benefits, but it should also reflect some Kantian imperatives and absolutes.”

But how are we to strike this magical balance between Bentham and Kant? And how are we to evaluate the multiplicity of factors and issues involved in preemptive war? Dershowitz does not say. By the book’s end, he seems to have thrown up his hands: he calls for a jurisprudence of prevention and preemption, recommends making adjustments based on future experience, and then withdraws.

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Some readers might find this pragmatic approach appealing because of its resemblance to the workings of the common law, which Dershowitz at times invokes as a source of inspiration and comparison. But the common law is not the only or even the most obvious way to approach the problem. He ignores, for example, the long tradition of just-war theory developed by Catholic thinkers and natural law philosophers. Nor does he engage modern academics such as Michael Walzer and John Rawls, each of whom wrote significant works on just-war theory. Dershowitz also neglects much that would have been relevant to his subject in the political thought of America’s founders. In The Federalist, for example, Alexander Hamilton observed that declarations of war had fallen into disuse because nations were then (1787) in the habit of launching unannounced attacks. He argued that the United States needed a strong presidency within a revitalized national government to protect itself against surprise attacks.

Dershowitz eschews American history, too. The United States, after all, has conducted several major wars that were arguably preemptive or preventive, including the Mexican-American War, the Spanish-American War, and World War I. In the first case, the U.S. reacted to a skirmish along the Texas border by invading Mexico and capturing its capital. America acted less in self-defense than preemptively to prevent Mexico or any other country from wielding power in the western half of the continent. Similarly, America responded to the destruction of the U.S.S. Maine by sinking Spain’s navy and seizing its overseas colonies. And though President Wilson could have sat out World War I, instead he launched a preventive war, as it were, against the rising power of Germany.

In the end, Dershowitz begs the basic question. He never explains why a “jurisprudence” of preemptive force is needed, or even whether one is possible. Decisions to use force depend upon the totality of the circumstances. No political entity exists to enforce international law, and nations regularly violate the U.N. Charter’s stipulations on the use of force. Preemption reflects a lawyerly overconfidence in the power of the law, a view unfortunately shared by the U.S. Supreme Court. It never occurs to Dershowitz to ask why, if the law really could work in this area, the legal rules already in place have failed so spectacularly.

He might have sought in Preemption to rethink how best to use military force in an age of terrorism. He might have drawn on our own history as well as the founders’ statesmanship while also engaging the serious philosophic and legal arguments that have been offered both for and against preemptive and preventive war. What he has given us instead is a series of talking points on hot-button issues. Somehow one expects more, even from Alan Dershowitz.