Take, for instance, the topic of warfare. When he was itemizing the precepts of the natural law, the jurist Gratian included on his list the idea that “violence should be repelled with force.” This looks like permission to wage war in self-defense—something most of us today would find reasonable enough. But we’re talking about philosophy in medieval Christendom, and didn’t Christ tell us to turn the other cheek? How, then, could Christian intellectuals give a rationale for the state’s use of violence?
