When in the Senate chamber, Ben Sasse, a Nebraska Republican, sits by choice at the desk used by the late Daniel Patrick Moynihan. New York’s scholar-senator would have recognized that Sasse has published a book of political philosophy in the form of a guide to parenting.

Moynihan understood that politics is downstream from culture, which flows through families. Sasse, a Yale history Ph.D. whose well-furnished mind resembles Moynihan’s, understands this:

America is a creedal nation made not by history’s churning but by the decision of philosophic Founders. Modern America, with its ene...