A commodity is, in the first place, a thing that satisfies some human need; in the second place, a thing that is exchanged for another thing. The usefulness of a thing makes it a use-value. Exchange-value (or simply value) is, first and foremost, a relation, a proportion in the exchange of a certain number of use-values of one kind for a certain number of use-values of another kind. Daily experience shows us that millions and billions of such exchanges constantly equate all and every kind of use-value, however diverse and incomparable to one another, with one another. What, then, is common to these different things that are constantly equated with one another within a definite system of social relations? What is common to them is that they are products of labor. In exchanging products, people equate the most diverse kinds of labor. Commodity production is a system of social relations in which individual producers create diverse products (the social division of labor), and all these products are equated with one another in exchange. Consequently, what is common to all commodities is not concrete labor of a particular branch of production, not labor of one kind, but abstract human labor, human labor in general. The entire labor-power of a given society, represented in the sum of the values of all commodities, is one and the same human labor-power: billions of exchange transactions prove this. And, consequently, each individual commodity represents only a certain portion of socially-necessary labor time. The magnitude of value is determined by the quantity of socially-necessary labor or the labor-time socially-necessary for the production of a given commodity, a given use-value. "In exchanging their diverse products for one another, people equate their diverse kinds of labor with one another. They are not conscious of this, but they do it"{67}. Value is a relation between two persons—as one old economist said; he should only have added: a relation cloaked in a material envelope. Only from the standpoint of the system of social productive relations of one definite historical form of society, and moreover relations manifested in the mass, repeatedly billions of times in the phenomenon of exchange, can one understand what value is. "As values, commodities are merely definite quantities of congealed labor-time"{68}. Having analyzed in detail the dual character of labor embodied in commodities, Marx proceeds to the analysis of the form of value and money. Marx's main task in doing so is to study the origin of the monetary form of value, to study the historical process of the unfolding of exchange, beginning with individual, accidental acts of it ("simple, singular, or accidental form of value": a given quantity of one commodity is exchanged for a given quantity of another commodity) up to the general form of value, when a series of different commodities is exchanged for one and the same definite commodity, and up to the monetary form of value, when this definite commodity, the universal equivalent, is gold. Being the highest product of the development of exchange and commodity production, money obscures and conceals the social character of private labors, the social connection between individual producers united by the market. Marx subjects the various functions of money to extraordinarily detailed analysis, and here too (as generally in the first chapters of *Capital*) it is particularly important to note that the abstract form of exposition, which sometimes seems purely deductive, actually reproduces a gigantic body of factual material on the history of the development of exchange and commodity production. "Money presupposes a certain degree of commodity exchange. The various forms of money—simple commodity equivalent or medium of circulation or medium of payment, treasure and world-money—indicate, depending on the different extent of application of one or another function, according to the comparative predominance of one of them, very different stages of the social process of production" (*Capital*, I){69}.