The exchange cannot be effected in kind; so what does Paul do?
He first exchanges his coat for some money, which is called _sale_; then he exchanges this money again for the things which he wants, which is called _purchase_; and now, only, has the reciprocity of services completed its circuit; now, only, the labor and the compensation are balanced in the same individual,--"I have done this for society, it has done that for me." In a word, it is only now that the exchange is actually accomplished.

Thus, nothing can be more correct than this observation of J.B.

Say: "Since the introduction of money, every exchange is resolved into two elements, _sale_ and _purchase_.

It is the reunion of these two elements which renders the exchange complete." We must remark, also, that the constant appearance of money in every exchange has overturned and misled all our ideas; men have ended in thinking that money was true riches, and that to multiply it was to multiply services and products.

Hence the prohibitory system; hence paper money; hence the celebrated aphorism, "What one gains the other loses;" and all the errors which have ruined the earth, and imbrued it with blood.[17] After much research it has been found, that in order to make the two services exchanged of equivalent value, and in order to render the exchange _equitable_, the best means was to allow it to be free.