As Marx put it, Ricardo's explanation passed from the field of political economy to chemistry. He showed, contrary to Ricardo, that the tendency of the rate of profit to fall arose not from the decreasing productivity of labour but rather from its increase. Labour is the sole source of surplus value. It would be wrong to conclude from the foregoing points that Marx simply took over the labour theory of value from Ricardo, making some amendments and improvements. The basis of this critique is referred to in Capital .
Every society has the task of allocating social labour in order to maintain it.
These individual producers, however, are not producing for their own subsistence, their production is social. It is regulated by, and can only be regulated by, the relationship of commodities, things, the products of labour. Only under very specific conditions does the product of labour take the form of a commodity which is exchanged in the market. In a primitive society, for example, there is a division of labour and different products of labour, but these products do not take the form of commodities. The members of the tribe do not share in the products of labour according to labour time they have contributed.