William Ruger makes "The Case for Realism and Restraint" (page 29). Ruger, 43, is an assistant professor of political science at Texas State University and a scholar at the Mercatus Center, where he co-wrote Freedom in the 50 States. He's also a veteran of the war in Afghanistan. Asked about America's biggest foreign policy mistakes, Ruger says "unnecessary wars deserve top billing." He points to conflicts in Iraq and Vietnam, adding that "the recent intervention in Libya is underrated as a mistake."

Fernando R. Tesón says "Don't Underestimate the Costs of Inaction" on page 34. Tesón, 64, is a professor at Florida State University College of Law. He's the author of the forthcoming Justice at a Distance (Cambridge University Press) with reason Contributing Editor Loren Lomasky. Tesón served for several years as a diplomat for Argentina's Foreign Ministry, but eventually resigned "to be an academic, and in protest against the human rights violations of the then-Argentine government," he says.

On page 32, Sheldon Richman argues that "Libertarianism Means Noninterventionism." Richman, 64, lives in North Little Rock, Arkansas, is vice president of The Future of Freedom Foundation, and edits its monthly publication, Future of Freedom. He's a longtime proponent of noninterventionism. "With Ron Paul's retirement, there is no clear and consistent voice for nonintervention," he says. "Considering the public support for new wars in Iraq and Syria, we can see that noninterventionism has not yet taken root."

Christopher Preble examines "Toward a Prudent Foreign Policy" (page 37). Preble, 47, is the vice president of defense and foreign policy studies at the Cato Institute. He is also the author of three books, including Terrorizing Ourselves: Why U.S. Counterterrorism Policy Is Failing and How to Fix It (Cato Institute). The biggest misconception about libertarian foreign policy, he says, is that it's "frequently mischaracterized as 'isolationist,' " which he calls "obviously incorrect." Libertarian reluctance about war "doesn't signal opposition to all wars, or to the use of force generally."