“Price is not the same thing as value. Suppose that on a day the price of everything viz., coal, bread, postage, stamps, a day’s labour, the rent of houses, etc. were to double. Prices then would certainly rise, but values of all things except one would not.” The writer wants to say that if prices of all things were doubled
the values of all things would remain constant.
the values of the things sold would be doubled.
the values of the things bought would be halved.
the value of money only would be halved.