The direct barter of products attains the elementary form of the
 relative expression of value in one respect, but not in another. That form
 is x Commodity A = y Commodity B. The form of direct barter is x use-value
 A = y use-value B.[5] The articles A and B in this case
 are not as yet commodities, but become so only by the act of barter. The
 first step made by an object of utility towards acquiring exchange-value
 is when it forms a non-use-value for its owner, and that happens when it
 forms a superfluous portion of some article required for his immediate
 wants. Objects in themselves are external to man, and consequently alienable
 by him. In order that this alienation may be reciprocal, it is only necessary
 for men, by a tacit understanding, to treat each other as private owners
 of those alienable objects, and by implication as independent individuals.
 But such a state of reciprocal independence has no existence in a primitive
 society based on property in common, whether such a society takes the form
 of a patriarchal family, an ancient Indian community, or a Peruvian Inca
 State. The exchange of commodities, therefore, first begins on the boundaries
 of such communities, at their points of contact with other similar communities,
 or with members of the latter. So soon, however, as products once become
 commodities in the external relations of a community, they also, by reaction,
 become so in its internal intercourse. The proportions in which they are
 exchangeable are at first quite a matter of chance. What makes them exchangeable
 is the mutual desire of their owners to alienate them. Meantime the need
 for foreign objects of utility gradually establishes itself. The constant
 repetition of exchange makes it a normal social act. In the course of time,
 therefore, some portion at least of the products of labour must be produced
 with a special view to exchange. From that moment the distinction becomes
 firmly established between the utility of an object for the purposes of
 consumption, and its utility for the purposes of exchange. Its use-value
 becomes distinguished from its exchange-value. On the other hand, the quantitative
 proportion in which the articles are exchangeable, becomes dependent on
 their production itself. Custom stamps them as values with definite magnitudes.