If all the exchange-ratios of the past were erased from human memory, the process of market-price-determination might certainly become more difficult, because everybody would have to construct a new scale of valuations for himself; but it would not become impossible. In fact, people the whole world over are engaged daily and hourly in the operation from which all prices result: the decision as to the relative significance enjoyed by specific quantities of goods as conditions for the satisfaction of wants.

The Theory of Money and Credit