One need not be an economist to figure out that, while all currencies can (and do) depreciate against something else (like gold, land, and other real assets), by definition they cannot all weaken against each other. In order for some currencies to depreciate, others must appreciate.
我们不需要成为一个经济学家就能明白，货币能（或者确实）对其他资产（比如黄金、土地和其他不动产）贬值，但显然它们不能全体一起相互贬值。某些货币贬值，其他货币则必然会相对升值。因此事情也就变得有趣、复杂且隐含潜在的风险。