Finally, when it is a matter of linking the representation of some object of need to all the others that can confront it in the act of exchange, it is necessary to have recourse to the form and quantity of a piece of work, which determine its value; what creates a hierarchy among things in the continuous circulation of the market is not other objects or other needs; it is the activity that has produced them and has silently lodged itself within them; it is the days and hours required for their manufacture, extraction, or transportation that constitute their proper weight, their marketable solidity, their internal law, and thus what one can call their real price; it is on the basis of this essential nucleus that exchanges can be accomplished and that market prices, after having ﬂuctuated, can find their point of rest.