It would seem, from all study of the essentials of money (Book III, Chapter IV), that the necessary part of the idea of money is that it should have value in itself. No one parts with valuable commodities for a medium of exchange which does not possess value; and we have seen that Legislatures can not control the natural value of even the precious metals by giving them legal-tender power. Much less could it be done for paper money. Paper, therefore, may, as an instrument of credit, be a substitute for money; but, in accordance with the above test, it can not properly be considered as money in the full sense. Of course, paper money, checks, etc., perform some of the functions of money equally well with the precious metals. F. A. Walker holds that anything is money which performs money-work; but he excludes checks from his catalogue of things which may serve as money. It is practically of little importance, however, what we include under money, so long as its functions are well understood; it is merely a question of nomenclature, and need not disturb us. Chapter X. Of An Inconvertible Paper Currency. § 1. What determines the value of an inconvertible paper money? After experience had shown that pieces of paper, of no intrinsic value, by merely bearing upon them the written profession of being equivalent to a certain number of francs, dollars, or pounds, could be made to circulate as such, and to produce all the benefit to the issuers which could have been produced by the coins which they purported to represent, governments began to think that it would be a happy device if they could appropriate to themselves this benefit, free from the condition to which individuals issuing such paper substitutes for money were subject, of giving, when required, for the sign, the thing signified. They determined to try whether they could not emancipate themselves from this unpleasant obligation, and make a piece of paper issued by them pass for a pound, by merely calling it a pound, and consenting to receive it in payment of the taxes. In the case supposed, the functions of money are performed by a thing which derives its power of performing them solely from convention; but convention is quite sufficient to confer the power; since nothing more is needful to make a person accept anything as money, and even at any arbitrary value, than the persuasion that it will be taken from him on the same terms by others. The only question is, what determines the value of such a currency, since it can not be, as in the case of gold and silver (or paper exchangeable for them at pleasure), the cost of production.