" For the correct Marxist classification of the proletariat-the class which is forced by socio-economic compulsion to sell its labour-power to the capitalist owners of the means of production – implies that both variations in the level of the reserve army of labour, and the variegated relations between the ‘purely physiological’ and ‘moral-historical’ components of the value of labour-power,63 are of decisive importance for the proletarian’s immediate destiny. "

― Karl Marx , Capital: A Critique of Political Economy, Volume 2