48 SOCIAL SCIENTIST two possibilities. In society as a whole, the working class produces a certain total mass of surplus value., and this surplus value is appropriated by the capitalist class. Now., the capitalists among themselves can consume immediately the entire surplus value. In this case, the total stock of means of production at the disposal of society remains the same as at the start of the production period, and social production can (given certain other conditions to be examined later on) be carried on at the same scale as before. In other words, there is no expansion (or contraction) of the economy, and we have what Marx calls simple reproduction. On the other hand, the capitalist class may not spend the entire surplus value in immediate consumption, but only a part of it. The remainder may be employed by the capitalist class in expanding production in order to reap more surplus value. In this case, leaving aside the part of surplus value expended in individual consumption by the capitalist class, the remainder, consisting partly of means of production and partly of means of subsistence for new workers to be hired, is ^invested5 in production^ that is, a part of surplus value is converted into (new) capital. We have here expanded reproduction or ^conversion of surplus value into capital." In what follows we discuss first, simple reproduction, and then conversion of surplus value into capital. Simple Reproduction Social reproduction is nothing but social production viewed in its continual repetition. Let us first view reproduction in physical terms, that is, in terms of the reproduction of goods and services. Each year, a certain amount of means of production is used up in the process of social production.1 Thus machinery gets depreciated to a certain extent, raw materials such as fuel get consumed and so on. In addition the workers who perform the labour by means of which social production takes place also expend their labour-power in this process. For physical reproduction to take place at the same level as before, the means of production to the extent that they have been used up and the goods and services required to reproduce the labour-power of all the workers must be produced afresh. While simple physical reproduction implies only replacement of used-up means of production and the production of 'subsistence5 for workers, social reproduction implies more. Viewing the capitalist labour process from the standpoint of social reproduction, not only must the value advanced be reproduced, but surplus value as well. Capitalist reproduction implies production of surplus value. This surplus value constitutes the ''revenue5 (income) of the capitalist class. With simple reproduction, the capitalist class spends the entire surplus value that it appropriates from the working class in individual and unproductive consumption.2 Simple reproduction, as reproduction, acquires a character quite