The Preventive State: The Challenge of Preventing Serious Harms While Preserving Essential Liberties
By Alan Dershowitz.
Encounter Books, 2025.
Hardcover, 240 pages, $29.99
Reviewed by Cary Federman.
In the late 1960s, Alan Dershowitz, the Felix Frankfurter Professor of Law, Emeritus, at Harvard Law School, began writing about preventive detention, a theme he continued to pursue during the early 1970s. He returned to the problem of dangerousness and prevention in a 2004 article on torture warrants (which he revisited for a 2008 book on terrorism), where he proposed that, if federal officials were to engage in torture (in light of events following 9/11), only the Chief Justice of the Supreme Court could issue a warrant detailing acceptable procedures. Dershowitz’s latest book, The Preventive State, is an attempt to formulate a jurisprudence for what he calls “mistake preferences.” That is, trying to solve or limit the problem of convicting the innocent and acquitting the guilty. “It is remarkable,” he writes, that “no systematic jurisprudence” of prevention “has ever been constructed to govern and constrain preventive measures.” In a previous book on the law of interrogation in the aftermath of 9/11, Dershowitz had called for such a jurisprudence, but no one answered the call.
What does a preventive jurisprudence look like? Readers of The University Bookman will immediately sense the presence of utilitarianism in such an inquiry. Prevention requires assessing costs and benefits, as well as determining risks and probabilities. Is it worth torturing a person who knows where a bomb is to prevent the deaths of hundreds, knowing that torture is illegal and may not produce accurate results? An “act utilitarian,” one who favors the greatest good for the greatest number of people, will say yes. A “rule utilitarian,” one who imposes an ethical theory on top of utilitarianism, will say no.
Alan Dershowitz is not an explicit follower of utilitarianism. He briefly mentions the founders of utilitarianism—Jeremy Bentham, John Stuart Mill, and Cesare Beccaria (there is no mention of James Mill)—only to refrain from discussing their ideas in any depth. Although it cannot be said that Dershowitz is a critic of utilitarianism, he bases his source for understanding prevention on “experience,” about a problematic legal principle as there could be.
The idea that experience should guide legal interpretation comes from an 1881 work by Oliver Wendell Holmes, Jr. In The Common Law, Holmes wrote: “The life of the law has not been logic: it has been experience.” Holmes wrote The Common Law as a practicing lawyer. But in short order, he would become a Harvard law professor, then a judge on the Massachusetts Supreme Judicial Court, and finally, one of the most influential justices on the U.S. Supreme Court, particularly on matters involving free speech. Holmes is known for his pragmatism. Legal pragmatists deny the possibility that correct outcomes can be derived from formal or universal principles found either in statutes or customs. Instead, they focus on the judge’s experience with the law. Legal pragmatists emphasize context and find legal meaning to be unformed and lacking foundation. Pragmatism is related to utilitarianism, but legal pragmatists differ from Benthamite utilitarians in that legal pragmatists favor a historical (and progressive and subjective) approach to legal problems, whereas Bentham wanted to codify the law to limit judge-made law.
Dershowitz does not address these details; his book takes a different approach. Mixing experience with “balancing”—the idea that judges must weigh the pros and cons of a legal problem by attributing to ideas or interests a value—Dershowitz puts forth a jurisprudence of prevention. He embraces Holmes’s idea that “prevention” and not retribution—the idea of just deserts—is “to be the chief and only universal purpose of punishment.” And he argues that the judge’s role is to balance the rights of the terrorist or the criminal against the public safety.
To understand how to prevent or limit harm, Dershowitz relies on what statisticians call error analysis. This involves classifying problems by the terms: true and false positives, and true and false negatives. Dershowitz provides a classic example of whether a judge should grant bail to an accused person. If a judge denies bail because he believed the accused might flee, but the accused would not have fled if released, this is a false positive—a mistaken prediction that someone would flee. Conversely, if the judge grants bail, assuming the accused will appear in court, but the accused flees, this is a false negative—a mistaken belief that the person would comply, which poses a risk to public safety. The question then becomes: how many false positives and false negatives can a society endure?
To answer that question, Dershowitz divides his book into three parts. In Part I, Dershowitz defines the terms and provides historical and contemporary examples. In Part II (chapters 2 through 12), Dershowitz provides 11 examples of the problems the government has encountered but has not solved. And in Part III, Dershowitz attempts to lay out his jurisprudence of prevention.
Part II is the heart of the book. Dershowitz offers examples such as preventing assassination, terrorism, ecological disasters, medical problems, such as vaccines and public health, and harmful speech. The examples offered are engaging to read. Dershowitz likes to pepper his narrative with real-life examples, as well as Borscht-belt humor, and personal reminiscences.
But I also found myself asking whether Dershowitz intended the chapters to be descriptive or prescriptive (or perhaps both). In some chapters, like the one on presidential assassinations, Dershowitz comes up with real proposals for changing how the Secret Service operates. But streamlining the Secret Service’s jurisdiction will not “prevent presidential assassinations,” as the chapter title reads. This is patchwork, not pragmatism. In his chapter on preventing crime, apart from calling for governmental subsidies for electronic surveillance and urging that judges balance “security and liberty” in the face of contradictory predictive assessments, I do not know what his solution is. And the same can be said of his chapter on speech. Here, Dershowitz writes that it is better to allow Nazis, communists, and pornographers to speak or march than the alternative, which is preventing them from doing so. But he never says why it is better, or whether a mild form of censorship—or regulation—is possible, instead of the more absolute kind he has in mind. Because he is focused on a progressive interpretation of rights, he never considers what the deliberate sense of the community might produce that could balance rights (or protect community safety) in ways better than judges can. “We must balance those risks in a manner that favors speech over fear,” he writes, without explaining why he thinks banning Nazi marches is an illegitimate fear, or how, exactly, judges can balance fear and rights.
Dershowitz admits the jurisprudence of risk assessment is a “daunting task,” one that judges should keep trying to refine. And so, in Part III, Dershowitz proposes ratios on a sliding scale for judges to consider when determining sentencing or bail. But he denies that such ratios should apply in speech cases, as the harm to public safety is low, he says. And in terrorism cases, he offers no specific ratio, but writes that “it is better that ten acts of terrorism be tolerated than that even one act of torture be authorized,” the exception being unless the false negative leads to “mass casualties.”
One must praise Dershowitz for venturing into this thorny problem and attempting to resolve it in favor of liberty. This is a thoughtful book and worthwhile for anyone interested in these complex issues. As I am not a judge, I cannot assess the usefulness of Dershowitz’s ratios for judges, although Dershowitz makes a compelling case for them, even as he admits they are heuristic. But in a broader sense, how can a judge’s personal (and historical) experiences lead to notions of constancy in law, so as to minimize false negatives? Wouldn’t experience, because it is subjective and of uncertain provenance, lead to constant variability in judicial outcomes? By not confronting his own beliefs, Dershowitz obscures just how much legal pragmatism, and the progressive and utilitarian ideas it is based on, undermines “the biblical command: justice, justice shall you pursue,” with which Dershowitz ends his book.
Cary Federman received his Ph.D. in Political Science from the University of Virginia. He teaches at Montclair State University. His most recent book is Democracy and Deliberation: The Law and Politics of Sex Offender Legislation (University of Michigan Press, 2021).
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