Marx propounded the theory of surplus value in order to explain the structure of the existing capitalist society, the nature of class antagonism and war and the reason why it will change into a socialist society of the future. Labour, says Marx, is a commodity, whose value is determined in the same way as that of other commodities. Its exchange-value is the amount of labour spent to produce it and maintain it, that is, the amount of the commodities required to feed, clothe and maintain the labourer. But the labour docs not receive exact amount of the exchange-value of his labour in the capitalist system. This is because he possesses only his labour power, but docs not own the means and methods of production, the tools and machines, raw materials and the like to expend his labour on them and produce commodities.<\/p>