My specialty is American history, but graduate school forces you to learn other branches of history as well, so it was not any great struggle to teach Western civilization. Still, when I do teach a class outside my concentration, I spend some time reading recent scholarship as well. If a student asks a question beyond what the textbook covers, it helps to be sufficiently well read in the field not to look stupid!
The debates at the Philadelphia Convention, and the war of pamphlets concerning ratification of the Constitution, make frequent reference to the problem of how and why republics die — and Rome was certainly one of the more common examples. One of the arguments against replacing the Articles of Confederation with an all-powerful national government was that republics on such a vast scale in people and area were impractical — and Rome was regarded as an example of this. Hence, our Constitution created a national government of limited powers. (And then it evolved, rather like an iguana turning into T. rex.)
Some of my recent background reading includes Christopher S. Mackay’s The Breakdown of the Roman Republic: From Oligarchy to Empire (2009). The introduction includes a description of what the Roman historian Sallust, writing The Catilinarian Conspiracy in the 30s BC, saw as the cause of the fall. The Roman republic had successfully defeated its only real serious mortal threat, Carthage, in the Punic Wars, but now:
Peace and wealth — things that are otherwise desirable — were an oppressive cause of misery for those who had easily endured hard work and danger and events both doubtful and dire. For this reason, there grew a greed first for money and then for rule, and these were like the raw material for all evils. For avarice overthrew good faith, honesty and all the other virtues, and in place of them it taught arrogance, cruelty, neglect of the gods, and the notion that everything is for sale. Self-serving ambition forced many men to become false,… to consider their friendships and enmities not on the basis of fact but of advantage, and to keep their countenance good rather than their character.
I suspect that when you read it, you will find yourself having the same reaction that my students did when I read it to them. Does this sound familiar? It seems like an awful lot went wrong when the last existential threat to our existence, the Soviet Union, quietly went out of business in 1991.
There are other disturbing parallels. Roman law provided for divorce, by some accounts, from the very beginning of the Roman republic in 509 BC. But it appears to have been extremely rare until the last several decades before the republic’s collapse. Yet by the end, it had become depressingly common, with even a respected statesman such as Cicero divorcing his wife of thirty years so that he could marry a rich heiress.