I vaguely recall from Gibbon, or maybe it was from a high school class, that the Roman Empire didn’t go out with a bang. With a nod to Alaric and his Visigoths of 410 AD, there really isn’t a singular event to mark the beginning of the long slide. In broad strokes it is fair to say that Roman society declined together, simultaneously with government. For centuries, Roman citizenship was a precious possession, a jewel of unsurpassed value. As such it was held closely and kept in short supply, for among other privileges, the Roman citizen wasn’t taxed. He was...