For Pietro Manes the argument regarding the real and value aspects of the production process arises from the fact that both Marxian and Classical economists are searching for a common or unifying factor between them, and this appears to be a mistake. According to Professor Manes, the two aspects cannot be unified. On the one hand, there is cost which can actually be reduced to the labor incorporated in the product while, on the other hand, there is value, which is not immediately related to cost. Value and cost are two different magnitudes which, at any given time, are absolutely independent of each other. At any given moment, the most costly product may have absolutely no value if no one needs or requests it, and conversely, a free good, such as natural water, may assume the greatest economic value in particular circumstances. The two magnitudes become elastically linked only in the dynamic process and, inasmuch as value is higher than cost, a productive process will be set in motion which, after a certain period of time, will be able to supply enough of the needed product to the market so that value reduces to the level of cost, and sometimes even below it (which requires an adjustment in the opposite direction and a certain period of time). The essence of the production process lies in this interplay between value and cost.