What would have happened if JFK survived that fateful Friday in Dallas? Or if the South won at Gettysburg? These questions have inspired film and literature, exploring the fascinating territory of “the what-ifs of history.” At the same time, there is a healthy debate among contemporary historians arguing whether alternate history is merely an entertaining distraction or a valuable tool to better appreciate that the paths of history are, in fact, far from inevitable. Indeed, there is actually a rich tradition of considering counterfactuals that can be demonstrated in the works of a number of ancient Roman historians (including Plutarch...