对于什么是货币,经济学家的认识在不断变化。在每一个时代,经济学家对货币的定义和理解都是有理有据的,但仍超脱不了他们的时代。例如马克思,尽管他提出了“货币天然不是金银,金银天然就是货币”的妙论,但他既没看到美元在国际货币体系的霸权地位崛起,更不会想象到由电脑里P2P软件算出的比特币将会掀起的热潮。 As for what is money, economists’ understanding is constantly changing. In every age, economists have well-founded definitions and understandings of money, but they still can not get away with their time. For example, Marx proposed that although “money is naturally not gold and silver, gold and silver are naturally currencies,” he did not see the rise of the dollar in the hegemony of the international monetary system, not to imagine that in the computer P2P software calculated bitcoin will set off a craze.