In the third chapter we have established that man cannot exist in a state of isolation. But if, by an effort of imagination, we fancy him placed in that chimerical situation, that state ‹contrary to nature›, which the writers of the eighteenth century extolled as the ‹state of nature›, we shall not fail to see that it does not disclose to us the idea of Value, although it presents the manifestation of the active principle which we have termed ‹effort›. The reason is obvious. Value implies comparison, appreciation, ‹estimation›, measure. In order that two things should measure each other, it is necessary that they be commensurable, and, in order to that, they must be of the same kind. In a state of isolation, with what could we compare effort? With want? With satisfaction? In that case, we could go no farther than to pronounce that the effort was more or less appropriate, more or less opportune. In the social state, what we compare (and it is this comparison which gives rise to the idea of Value) is the effort of one man with the effort of another man,—two phenomena of the same nature, and, consequently, ‹commensurable›. Thus, the definition of the word Value, in order to be exact, must have reference not only to human efforts, but likewise to those efforts which are exchanged or exchangeable. Exchange does more than exhibit and measure values—it gives them existence. I do not mean to say that it gives existence to the acts and the things which are exchanged, but it imparts to their existence the notion of ‹value›. Now, when two men transfer to each other their present efforts, or make over mutually the results of their anterior [p135] efforts, they ‹serve› each other; they render each other reciprocal ‹service›. I say, then, «Value is the relation of two services exchanged». The idea of ‹value› entered into the world the first time that a man having said to his brother, Do this for me, and I shall do that for you—they have come to an agreement; for then, for the first time, we could say—The two ‹services› exchanged are ‹worth each other›. It is singular enough that the true theory of value, which we search for in vain in many a ponderous volume, is to be found in Florian’s beautiful fable of ‹l’Aveugle et le Paralytique›,— Aidons—nous mutuellement, La charge des malheurs en sera plus légère.   . . . . . . . A nous deux Nous possédons le bien à chacun nécessaire. J’ai des jambes, et vous des yeux. Moi, je vais vous porter; vous, vous serez mon guide: Ainsi, sans que jamais notre amitié décide Qui de nous deux remplit le plus utile emploi, Je marcherai pour vous, vous y verrez pour moi.