... One of the privileges typically claimed by the imperial president is the right to the"necessary lie." In matters of national security, the thinking goes, the public is often too dense to understand the realpolitik of international relations, the hard choices and messy compromises of war and peace. A well-timed lie can shield a good policy from the condemnation of a foolish electorate and galvanize public opinion behind a wise but politically unpopular course of action. Deception thus becomes a president's patriotic duty.

With our current quagmire in Iraq at least partially a result of the Bush administration's dissimulation and deceit, such thinking is out of fashion. But history offers examples that are less easily condemned. Would anyone fault Franklin Roosevelt for his expressed willingness to"mislead and tell untruths" when faced with an isolationist public too complacent to take up arms against Hitler? Eric Alterman, for one, does in"When Presidents Lie," a study of four cases of presidential deception in the name of the national interest. Alterman, a muckraking historian best known for his column in the Nation, denounces the myth of the"noble lie" as a sham perpetrated on the public by a cowardly, arrogant, self-serving political elite -- with invariably disastrous results.

Two of Alterman's case studies level well-rehearsed charges at notorious acts of deceit: Lyndon Johnson's escalation of the U.S. presence in Vietnam and Ronald Reagan's systematic duplicity regarding U.S. involvement in Central America. The other two examples -- more provocative but less convincing -- take on heroic targets. Franklin Roosevelt's misrepresentation of the agreement he struck with Stalin at Yalta in 1945, Alterman contends, sowed in the American populace (which wrongly believed that Stalin was violating the terms of the deal) a distrust of the Soviet Union that led to the Cold War. John F. Kennedy's refusal to acknowledge the tacit missile swap that helped end the Cuban missile crisis, similarly, gave Americans an unreasonable expectation of presidential bravado and thus brought on a host of subsequent Cold War conflicts and crises.

Invoking pragmatism rather than principle, Alterman sets out to prove that under no circumstances is the"necessary lie" permissible. It not only erodes public trust in government, he argues, but also, by giving a lie's victims and its perpetrators a skewed view of reality, leads to foreign policy disasters that otherwise could have been avoided. While much of this case is closely and adeptly argued, Alterman overreaches on this second point, resorting to some extravagant logical leaps (to prove, for example, that Roosevelt's dishonesty was itself a principal cause of the Cold War)."When Presidents Lie" also suffers from excessive present-mindedness. Alterman insightfully points out that presidential deceit is almost always motivated by domestic political considerations despite the national security rhetoric in which it is veiled. But he chastises leaders for caving into such pressures without acknowledging just how overpowering such political constraints can be.

Still, Alterman's basic point stands: Even seemingly justified lies have unintended consequences that expose the initial calculation of cost and benefit as tragically short-sighted.