Economic nationalism isn't a phrase typically uttered at the Conservative Political Action Conference, but White House chief strategist Steve Bannon spoke it three times in a brief panel discussion there on Thursday. The phrase is as ungraspable by itself as a bar of wet soap. In its most promising construction, it captures something important and right. But it fraught with pitfalls and perils that need to be avoided. It reflects long-ignored philosophical and political truths, but can also give...