So far, however, we have only considered the needs of man for currency; that is to say, for a medium of exchange for the time being. It is obvious, however, that any commodity which fulfils this function, that is to say, is normally taken in payment in the exchange of commodities and services, also necessarily acquires a still more important duty, that is, it becomes a standard of value, and it is on the alleged failure of gold to meet the requirements of the standard of value that the present attack upon it is based. On this point the defenders of the gold standard will find a good deal of difficulty in discovering anything but a negative defence. The ideal standard of value is one which does not vary, and it cannot be contended that gold from this point of view has shown any approach to perfection in fulfilling this function. It could only do so if the supply of it available as currency could by some miracle be kept in constant relation with, the supply of all other commodities and services that are being produced by mankind. That it should be constant with each one of them is, of course, obviously impossible, since the rate at which, for example, wheat and pig-iron are being produced necessarily varies from time to time as compared with one another. Variations in the price of wheat and pig-iron are thus inevitable, but it can at least be claimed by idealists in currency matters that some form of currency might possibly be devised, the amount of which might always be in agreement with the amount of the total output of saleable goods, in the widest sense of the word, that is being created for man's use.