Is there an enduring American character? For those who view our nation as at a tipping point, the question is urgent. Others scoff, “Why?” After all, if the American character is truly enduring, it will endure — the ship eventually will right itself to the extent it is off course. And if not, history will inevitably evolve it into something better, right? My friend Mark Levin would counter that this is the wrong way to look at it. The foundation of Americanism, he posits, is natural law. That does not just spontaneously appear, nor passively persevere. Understanding our natural-law roots,...