So Do Morals Matter in U.S. Foreign Policy? I Asked the Expert.

A new book by Joseph S. Nye Jr. suggests that for presidents, good intentions are not enough.

For college freshmen or incoming presidents, no international relations reading list would be complete without a few pivotal readings from Harvard Kennedy School Distinguished Service Professor Emeritus Joseph S. Nye Jr.

In his new book, "Do Morals Matter? Presidents and Foreign Policy from FDR to Trump," Nye developed a scorecard to determine how U.S. presidents since 1945 factored questions of ethics and morality into their foreign policy. I asked him a few questions to get to the heart of his findings.

HF: Your book asks how morality affects U.S. presidential decisionmaking over foreign policy. Left-wing critics of the United States suggest that morality plays little or no role in U.S. foreign policy. Realist critics suggest that it shouldn't play any role. What does the post–World War II historical record suggest?

JSN: The conventional wisdom in our field is that "interests bake the cake" and then politicians sprinkle a little moral icing on it to make it look pretty. By looking in detail at the 14 presidents since 1945, I show that in a number of instances, if you hold too simply to this cynical view, you are going to get the history wrong. Several crucial decisions, such as Truman's rejection of MacArthur's advice to use nuclear weapons in 1950, were strongly influenced by the president's moral views. And the world would look very different today had Truman decided differently....