Nevertheless, the struggle between good and evil remained in the world as a sad legacy of the original fall. Nor has the ancient tempter ever ceased to deceive mankind with false promises. It is on this account that one convulsion following upon another has marked the passage of the centuries, down to the revolution of our own days. (Papal Encyclical, Divini Redemptoris, 19 March 1937).
The total amount of evil in any system remains constant.