Thus, in the modified form C―M in which the commodity is present and money is only represented, money plays first of all the part of a measure of value. The exchange value of the commodity is estimated in money as its measure; but as exchange value, established by contract, price exists not only in the mind of the seller, but also as a measure of obligation on the part of the buyer. Besides serving as a measure of value, money plays here the part of a means of purchase, although in that capacity it only casts ahead the shadow of its future existence. It attracts the commodity from its position in the hand of the seller into that of the buyer. As soon as the term of the contract expires, money enters circulation, since it changes its position by passing from the hands of the former buyer into those of the former seller. But it does not enter circulation as a circulating medium or as a means of purchase. It performed those functions before it was present and it appears after it has ceased to perform them. It now enters circulation as the only adequate equivalent of the commodity, as the absolute form of existence of exchange value, as the last word of the process of exchange, in short as money, and money in its distinct role of a _universal means of payment_. In this capacity of a means of payment money appears as the absolute commodity, but within the sphere of circulation and not without it as was the case with hoards. The difference between the means of purchase and the means of payment makes itself unpleasantly felt in periods of commercial crises.[104] Originally, the conversion of the product into money in the sphere of circulation appears only as an individual necessity for the commodity owner in so far as his own product has no use-value to him, but has to acquire it first by being alienated. But in order to pay at the expiration of the contract, he must have sold commodities before that. Thus, entirely apart from his individual wants, the movement of the circulation process makes selling a social necessity with every owner of commodities. As a former buyer of a commodity he is compelled to become a seller of another commodity in order to get money not as a means of purchase but as a means of payment, as the absolute form of exchange value. The conversion of commodity into money as a final act, or the first metamorphosis of a commodity as an end in itself which in the case of hoarding seemed to be a matter of caprice on the part of the commodity owner, becomes now an economic function. The motive and essence of sale for the sake of payment becomes from a mere form of the process of circulation its self emanating substance.