Thomas Sowell said this quote
“ The monumental tragedies of the 20th century -- a world-wide Great Depression, two devastating World Wars, the Holocaust, famines killing millions in the Soviet Union and tens of millions in China -- should leave us with a sobering sense of the threats to any society. But this generation's ignorance of history leaves them free to be frivolous -- until the next catastrophe strikes, and catches them completely by surprise. ”