Before Oswald Spengler, Arnold Toynbee and other historians of cultural rise and fall, there was Brooks Adams. And while today there are ever more historians adding their theories as to why civilizations collapse through such factors as military invasion, over-taxation, or ecological shifts, most of these theories do not get to the cause of how civilizations, if not stunted and killed in youth or middle age, die of old age.

Our Western Civilization has an optimism that we have a culture of eternal life because of our science and industry, but it is precisely in this cycle of...