Suppose, for example, a house and a vessel of a value so perfectly equal that their proprietors are disposed to exchange them even-handed, without excess or abatement. In fact let the bargain be settled by a lawyer. At the moment of each taking possession, the shipowner says to the citizen, "Very well; the transaction is completed, and nothing can prove its perfect equity better than our free and voluntary consent. Our conditions thus fixed, I shall propose to you a little practical modification. You shall let me have your house to-day, but I shall not put you in possession of my ship for a year; and the reason I make this demand of you is, that, during this year of _delay_, I wish to use the vessel." That we may not be embarrassed by considerations relative to the deterioration of the thing lent, I will suppose the shipowner to add, "I will engage, at the end of the year, to hand over to you the vessel in the state in which it is to-day." I ask of every candid man, I ask of M. Proudhon himself, if the citizen has not a right to answer, "The new clause which you propose entirely alters the proportion or the equal value of the exchanged services. By it, I shall be deprived, for the space of a year, both at once of my house and of your vessel. By it, you will make use of both. If, in the absence of this clause, the bargain was just, for the same reason the clause is injurious to me. It stipulates for a loss to me, and a gain to you. You are requiring of me a new service; I have a right to refuse, or to require of you, as a compensation, an equivalent service." If the parties are agreed upon this compensation, the principle of which is incontestable, we can easily distinguish two transactions in one, two exchanges of service in one. First, there is the exchange of the house for the vessel; after this, there is the delay granted by one of the parties, and the compensation correspondent to this delay yielded by the other. These two new services take the generic and abstract names of _credit_ and _interest_. But names do not change the nature of things; and I defy any one to dare to maintain that there exists here, when all is done, a service for a service, or a reciprocity of services. To say that one of these services does not challenge the other, to say that the first ought to be rendered gratuitously, without injustice, is to say that injustice consists in the reciprocity of services,--that justice consists in one of the parties giving and not receiving, which is a contradiction in terms. To give an idea of interest and its mechanism, allow me to make use of two or three anecdotes. But, first, I must say a few words upon capital.