Leaving out of consideration, therefore, the physical qualities that give commodities use value, we find in them but one common characteristic—that they are all products of human labour. They are all crystallised forms of human labour. It is labour applied to natural objects that gives them value. What constitutes value is the human labour embodied in commodities. And the relation of exchange is only a phase of this value, which is therefore to be considered independently of it. Further, the labour time spent in producing value is the measure of value, not this or that individual labour, in which case a lazy or unskilled man would produce as great a quantity of value as the most skilful and energetic. We must take as our standard the average labour force of the community. The labour time which we take as the measure of value is the time required to produce a commodity under the normal social conditions of production with the average degree of skill and intensity of labour. Thus labour is both the source and the measure of value. The conditions necessary to the existence and growth of capitalism, therefore, are as follows:—A class, who have a virtual monopoly of the means of production; another class of labourers, who are free, but destitute of the means of production; and a system of production for exchange in a world market. But it may be asked how these historical conditions were established? How did the capitalist class originate, and how were the workers divorced from the instruments of labour, and how was the world market opened up? Such a state of things was established only after a long and gradual process of change, which Marx copiously illustrates from the history of England, as the classic land of the fully developed capitalism. In the Middle Ages the craftsman and peasant were the owners of the small means of production then extant, and they produced for their own needs and for their feudal superior; only the superfluity went into the general market. Such production was necessarily small, limited, and technically imperfect. Towards the close of the Middle Ages a great change set in, caused by a remarkable combination of circumstances—the downfall of the feudal system and of the Catholic Church, the discovery of America and of the sea route to India. Through the breaking-up of the feudal houses with their numerous retainers, through the transformation of the old peasant-holdings into extensive sheep-runs, and generally through the prevalent application of the commercial system to the management of land, instead of the Catholic and feudal spirit, the peasantry were driven off the land; a multitude of people totally destitute of property were thrown loose from their old means of livelihood, and were reduced to vagabondage or forced into the towns. It was in this way that the modern proletarians made their tragic entry in history.