Does classical liberalism suggest the kind of a foreign policy the United States should pursue? If classical liberalism rests on premises about human nature and the world, namely, that individuals in politics tend toward passion and self-interest and that governments have access to very incomplete information about most worldly matters, I think it does. The foreign policy of a state built on these principles should resemble its domestic policy, market-oriented with limited public goals, most importantly of course defending the nation from foreign threats.
Thus, while the details of foreign policy of any time depend on the constellation of threats and circumstances in the world, a constant should be its modesty. First, we know relatively little about the traditions and internal politics of most other nations, almost never enough to be confident of changing them dramatically to our advantage. Second, our own nation is riven by political factions in which each faction will criticize the other for partisan advantage. Thus, it is difficult to sustain over time a complicated foreign policy, particularly any that costs a lot of money, unless the threats are clear enough that they inspire unity. And our government is unlikely to carry out the details of even laudable but complex foreign policy objectives well for the same public choice reasons that have doomed so many domestic policies that seem admirable on first hearing.
That does not mean the a classically liberal foreign policy is an isolationist policy. As John Lewis Gaddis’ superb biography of George Kennan makes clear, the greatest foreign policy success of the latter half of the twentieth century was containment. It was an outward-looking policy by which the United States sought to prevent the Soviet Union from further domination by exploiting the regime’s patent vulnerabilities until the self contradictions of communism doomed it. The threat from the Soviet Union was clear enough and the policy modest enough that it commanded widespread support among both Democrats and Republicans with exception of a rather small band of anti anti-communist intellectuals.
The policy should also be market-oriented, encouraging trade among nations except when that trade is a danger to national security. International markets no less than national ones serve liberty and prosperity and international markets no less than domestic ones are not subject to the information problems of government decision-making. And there is empirical support of one of the oldest ideas of classical liberalism—the softening effect of commerce. As Montesquieu noted, “Peace is the natural effect of trade. Two nations who differ with each other become reciprocally dependent; for if one has an interest in buying, the other has an interest in selling; and thus their union is founded on their mutual necessities.” The policies of our founders was similar. The Model Treaty proposed with many nations after the Revolution sought free and reciprocal trade with other nations.
Of course, that market-orientation does not mean that nations that trade together cannot go to war. People have other passions than a desire for a prosperity. But it makes it less likely. Nor should this market orientation necessarily eliminate the use of trade sanctions against regimes, like Iran, that are substantial threat. But it should make us very doubtful about trade wars against our allies.
On this view, the last two Republican Presidents each captured at best only one of the two pillars of a classically liberal foreign policy. George W. Bush aggressively pursued freer trade, but often had overweening ambitions of transforming other nations. Trump is much more modest in such ambitions, but he has created substantial tensions in commerce among nations. Classical liberals still await a contemporary foreign policy champion no less than a domestic one.