A majority of the American people is telling pollsters it wants the U.S. government to keep out of other nations’ business, that it does not want America to be at war indefinitely, and that it fears the U.S. government’s growing “homeland Security” powers—including the power to declare any American to be a terrorist and to kill him—more than it fears terrorism. Because Kentucky Sen. Rand Paul has explained better than anyone why he shares these majority sentiments, he is halfway home to claiming foreign policy credibility for his 2016 presidential candidacy.

But only halfway, because the very same popular majorities also say they want the U.S. government to be much tougher against America’s enemies. Neither Paul nor any other candidate seems to have thought about what it would mean for the U.S. government to pull back from involvement in other peoples’ business, to make foreign commitments and conduct internal security according to the Constitution, while at the same time being tougher against our enemies. The establishment regards these sentiments as contradictory. In fact, they are complementary parts of the American people’s historic, coherent approach to international affairs. To be credible, Paul—or any other contender for the presidency—must figure out why this is so and how to apply this insight to our time’s pressing problems.

Herewith, some suggestions for Rand Paul.

How To Wield Both Sides of the Sword

Rightly, Paul decries the sterile confrontation between libertarians who suppose that erstwhile foreign enemies will leave us be once we turn our back to them, and neoconservatives who want to impose our order or our ways on mankind. Where, he asks, “are the Kennan’s [sic] of our generation?…Where are the calls for moderation, the calls for restraint?” This sounds Aristotelian. But moderation and restraint are meaningful only in relation to actual alternatives.

Rand Paul must give concrete examples of what he considers the extremes.

A medical doctor – an ophthalmologist by profession, and graduate of the Duke University School of Medicine – Paul may be excused for not having thought through the details of international affairs. Not so those whom he chooses as his advisers in the field. To be credible, he and they would have to give concrete examples of what they consider the extremes, and what the middle way might be—what they deem to be other people’s business and what our own. They have a ways to go.

For example, Paul’s major pronouncement on foreign affairs said: “Over 50% of Americans still believe Iraq attacked us on 9/11,” as if to accuse his fellow citizens of bellicose ignorance. But while no one knows the details of the extensive relationship between Saddam Hussein’s intelligence service and Khalid Sheik Mohammed, 9/11’s executor, there is no doubt that Saddam was a main engine of death to Americans. He had made himself the paladin of anti-Americanism, was running terrorist training camps and was paying terrorists, including those who carried out the first bombing of the World Trade Center.

Paul might have said that making an example of Saddam and his Ba’ath party by overthrowing them was necessary to America’s peace, but that occupying Iraq to try forcing peace among its factions was a counterproductive intrusion into their business. Our future moderation, he might yet say, would consist of undoing our enemies because of the harm they portend to us rather than to others. That is what the American people reasonably desire.

Paul’s pronouncements warn Americans that trying to de-nuclearize Iran through “pre-emptive bombing” would have “unintended consequences,” that “war should never be our only option,” and that “the debate over war is the most important debate that occurs in our country.” They stress, properly, that the Constitution puts Congress at the center of that debate. But the substance of his proposal for dealing with Iran and with radical Islam in general—some kind of “containment” based on “creative ambiguity” about what we might or might not do—is no substance at all.

Words Alone Mean Nothing

“Strategic ambiguity,” Paul admits, is “a policy of having no policy,” “a combination of don’t mess with us language and diplomacy.” Why should such substance-less language impress the Iranians, the Chinese, the Russians, or any of the Muslim potentates who incite terror against us? Paul answers: “The world knows we possess an enormous ability of nuclear retaliation…But for our enemies to be uncertain what provocation may awaken an overwhelming response, nuclear or conventional, is an uncertainty that still helps to keep the peace.”

For a generation, the U.S. government has been interfering in other peoples’ business while neglecting our own.

But even 60 years ago, when the world had far more reason to take America seriously than it does now, the Eisenhower administration’s threat to respond to Communist breaches of containment massively (i.e. with nukes) “at times and places of our own choosing” rang hollow. It lost the last vestiges of credibility when the U.S. government renounced plans to defend America against ballistic missiles and dismantled our air defenses.

In short: today, any number of people in the Muslim world are “messing with us,” while the Chinese and Russian governments are setting about doing so even more seriously. They feel safe in doing so. For a generation, the U.S. government has been interfering in other peoples’ business while neglecting our own—making commitments without consideration of what it would take actually to keep them. It has spoken loudly while whittling down America’s stick. We have earned disrespect. Today, nobody takes America seriously. Would-be President Paul has made clear that his America would speak much more softly. Good. But he seems to have given little thought about what kind of stick the U.S. government needs to secure America’s peace as well as about what strokes may be needed to restore respect.

Today, China is building a military reasonably designed to control the western Pacific Rim from land bases. How would President Paul counter that? China has warned that any serious attempt to safeguard the independence of the islands off its coast might lead to the nuclear destruction of American cities. Would President Paul defend America against Chinese missiles, or Russian ones? As Muslim potentates from Palestine to Pakistan consider whether to (send or allow, it matters not) any of their zealots to kill more Americans, what reason would President Paul give them to hold them back? If and when terrorists from country X strike America, what if anything would he do to those in power there? In the meanwhile, what would he do to signal seriousness? Would he continue to subsidize the Palestinian Authority’s nursery of anti-Americanism and anti-Semitism?

Paul‘s pronouncements on foreign policy, promising as they do retrenchment from foolish commitments, are faithful to the physician’s maxim: “First, do no harm.” But foreign affairs, as well as medicine, require more than refraining from harm. We may hope that Dr. Paul will study foreign affairs with the same seriousness with which he mastered medical school, and with equally competent professors.

Angelo M. Codevilla is professor emeritus of international relations at Boston University and the author of To Make And Keep Peace, Hoover Institution Press, 2014