Borepatch embedded a very short, but very interesting analysis by Kenneth Clark on why Rome fell. It's only two and a half minutes long, and well worth that much of your time to watch it.
Our modern civilization can fall, too, and in a surprisingly short time. It's happened right before our eyes multiple times over the past half-century. Think of the Soviet Union in the late 1980's, or Venezuela over the past five years. It could happen even to the USA or Western Europe, if enough of the storm clouds gathering over either economy were to let loose. (Think of what would happen if the US government, due to economic circumstances, were to stop providing Social Security and/or Medicaid to its citizens: or, alternatively, if we did not act to stop illegal alien infiltration, and they did to the whole of the US economy what they've already done to California. What would either and/or both of those events do to a very large part of our population? And what would that imply for our society as a whole?)
Food for thought.