(c) It only remains in this branch of the general discussion on Value, to indicate the Limits, within which all oscillations of Value are contained. These extreme limits are specially to be found in the element of Value which we have called "Efforts." We have clearly seen already, that "efforts" (or Labor) are not, as has been often asserted, the cause of Value, but only one of several constituent causes; if Labor be asserted to be the sole cause of Value, the inquiry becomes instantly pertinent, what is the cause of the value of Labor; yet we know, that "efforts" always stand in preconnection with value, and, the mutual "desires" being presupposed, there must always be Limitations of Value lying partly in the efforts made by the person serving and partly in the efforts saved to the person served. In every valuable transaction, each of the parties is reciprocally serving and served, and it is clear, that the two would not exchange "renderings" unless the service which each renders to the other is less onerous than the "efforts" which each would have to make if each served himself directly. For example, it takes a certain effort for me to bring water from the spring for the use of my family; I am willing to pay a neighbor for bringing it for me, but I should not be willing to make a greater effort for him in return than the effort is to bring it myself; neither should I be willing to make an effort for him in return which I regarded just as onerous as the bringing the water myself; and unless there is some service which he will accept less onerous to me than that, I shall continue to bring the water. On the other hand, he will surely not render the service to me of bringing the water, unless it be less onerous to him to do so than the doing that for himself which I am ready to do for him. This principle, applicable to all exchanges whatsoever, draws on the one side the outermost line, beyond which Value never can pass. It may be asserted with confidence, that no person will ever knowingly make a greater effort to satisfy a desire through exchange, than the effort needful to satisfy it without an exchange. Therefore, it follows, that all exchanges lessen onerous efforts among men relatively to the satisfaction of their desires, and tend to lessen these more and more as exchanges multiply in number and variety, otherwise the exchanges would not take place.