Nor is this all. Nothing is more easily explained than this pre-eminence, this priority, given to the service over the product, so far as value is concerned. We shall immediately see that this is owing to a circumstance which might have been easily perceived, but which has not been observed, just because it is under our eyes. It is nothing else than that foresight which is natural to man, and in virtue of which, in place of limiting himself to the services which are demanded of him, he prepares himself beforehand to render those services which he foresees are likely to be demanded. It is thus that the ‹facio ut facias› transforms itself into the ‹do ut des›, without its ceasing to be the dominant fact which explains the whole transaction. John says to Peter, I want a cup. I could make it for myself, but if you will make it for me, you will render me a service, for which I will pay you by an equivalent service. Peter accepts the offer, and, in consequence, sets out in quest of suitable materials, mixes them, manipulates them, and, in fine, makes the article which John wants. It is very evident that here it is the service which determines the value. The dominant word in the transaction is ‹facio›. And if, afterwards, the value is incorporated with the product, it is only because it flows from the service, which combines the labour executed by Peter with the labour saved to John. Now, it may happen that John may make frequently the same proposal to Peter, and that other people may also make it; so that Peter can foresee with certainty the kind of services which will be demanded of him, and prepare himself for rendering them. He may say, I have acquired a certain degree of skill in making cups. Experience tells me that cups supply a want which must be satisfied, and I am therefore enabled to manufacture them beforehand. Henceforth John says no longer to Peter, ‹facio ut facias›, but ‹facio ut des›. If he in turn has foreseen the wants of Peter, and laboured beforehand to provide for them, he can then say ‹do ut des›. [p175] But in what respect, I ask, does this progress, which flows from human foresight, change the nature and origin of value? Does service cease to be its foundation and measure? As regards the true idea of value, what difference does it make whether Peter, before he makes the cup, waits till there is a demand for it, or, foreseeing a future demand, manufactures the article beforehand?