Yet such a boom, artificially engineered by monetary and credit expansion, cannot last forever. It must come to an end sooner or later. For paper money and bank deposits are not a proper substitute for non-existing capital goods. Economic theory has demonstrated in an irrefutable way that a prosperity created by an expansionist monetary and credit policy is illusory and must end in a slump, an economic crisis. It has happened again and again in the past, and it will happen in the future, too.