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 embrued it with blood.[2] 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. However plausible, at first sight, the intervention of the State might be, it was soon perceived that it is always oppressive to one or other of the contracting parties. When we look into these subjects, we are always compelled to reason upon this maxim, that _equal value_ results from liberty. We have, in fact, no other means of knowing whether, at a given moment, two services are of the same value, but that of examining whether they can be readily and freely exchanged. Allow the State, which is the same thing as force, to interfere on one side or the other, and from that moment all the means of appreciation will be complicated and entangled, instead of becoming clear. It ought to be the part of the State to prevent, and, above all, to repress artifice and fraud; that is, to secure liberty, and not to violate it. I have enlarged a little upon exchange, although loan is my principal object: my excuse is, that I conceive that there is in a loan an actual exchange, an actual service rendered by the lender, and which makes the borrower liable to an equivalent service,--two services, whose comparative value can only be appreciated, like that of all possible services, by freedom. Now, if it is so, the perfect lawfulness of what is called house-rent, farm-rent, interest, will be explained and justified. Let us consider the case of _loan_.