circulation as a whole: once the process of circulation is concluded, money will always have returned to its point of origin. Thus all capitalists, after universal exchange, have achieved a twofold result: first they have exchanged products which, in their natural form, were of no use to them, against other products which, in their natural form, the capitalists require either as means of production or for their own consumption. Secondly, they have regained possession of the money which they set in circulation so as to effect these acts of exchange. This phenomenon is unintelligible from the point of view of simple commodity circulation, where commodity and money continually change places--possession of the commodity excluding the possession of money, as money constantly usurps the place which the commodity has given up, and _vice versa_. Indeed, this is perfectly true with regard to every individual act of commodity exchange which is the form of social circulation. Yet this social circulation itself is more than mere exchange of commodities: it is the circulation of capital. It is, however, an essential and characteristic feature of this kind of circulation, that it does not only return to the capitalist the value of his original capital plus an increase, the surplus value, but that it also assists social reproduction by providing the means of production and labour power in the natural form of productive capital, and by ensuring the maintenance of those who do not work. Possessing both the means of production and the money needed, the capitalists start the total social process of circulation; as soon as the social capital has completed its circuit, everything is again in their hands, apportioned to each department according to the investments made by it. The workers have only temporary possession of money during which time they convert the variable capital from its money form into its natural form. The variable capital in the capitalists' hands is nothing but the outward shape of part of their capital, and for this reason it must always revert to them.