These things are all tragic. Human rights are good. Democracy is good. America is good. But that does not mean that the good can always and everywhere be achieved, or that we can take the straightest path to the good. Our foreign policy must have, in the words of the famous “Serenity Prayer,” “the courage to change the things we can.” But it must also learn “the serenity to accept the things we cannot change” and “the wisdom to know the difference.” That Cruz rejects nation building does not mean he has found that wisdom. He has not yet found a foreign policy of realistic, conservative, “merely human” purposes.

The problem with idealism like Cruz’s, as conservatives have been arguing for centuries, is that it often fails to achieve its aims, and in failing only makes things worse. That’s what would likely happen if the United States took Cruz’s advice on Iran and Ukraine. Will holding out on nuclear talks until Iran takes the most pro-Israel position in the Muslim world make it more or less likely that we will reach a deal that arrests Iran’s nuclear progress? Will isolating Iran and vindicating the Iranian hardliners who have said that America cannot be trusted make the human-rights situation there better, or worse? Will renewed confrontation make it more likely that those Americans held in Iran will be freed? Will pushing for total victory in Ukraine make Russia bow, or will it only deepen the crisis, with grave consequences for all? Such practical considerations seem to have gotten little airtime in chez Cruz. “History,” said Ambassador Kirkpatrick in that old Commentary article, “is a better guide than good intentions.” One hopes Senator Cruz—or at least one of his interns—will take that line to heart.

John Allen Gay is an assistant managing editor at The National Interest. His book (co-authored with Geoffrey Kemp) War with Iran: Political, Military, and Economic Consequences was released by Rowman and Littlefield in early 2013. He tweets at @JohnAllenGay.

Image: Gage Skidmore, CC BY-SA 2.0.