3i8 KARL MARX: A BIOGRAPHYinto capital. Before the capitalist era people had sold commodities for
money in order to buy more commodities. In the capitalist era, instead
of selling to buy, people had bought to sell dearer: they had bought
commodities with their money in order, by means of those commodities,
to increase their money.
In the third section Marx introduced his key notion of surplus value,
the idea that Engels characterised as Marx's principal 'discovery' in eco-
nomics.^194 Marx made a distinction between constant capital which was
'that part of capital which is represented by the means of production, by
the raw material, auxiliary material and instruments of labour, and does
not, in the process of production, undergo any quantitative alteration of
value' and variable capital. Of this Marx said: 'That part of capital, repre-
sented by labour power, does, in the process of production, undergo an
alteration of value. It both reproduces the equivalent of its own value,
and also produces an excess, a surplus value, which may itself vary, may
be more or less according to the circumstances.'^195 This variation was the
rate of surplus value around which the struggle between workers and
capitalists centred. The essential point was that the capitalist got the
worker to work longer than was merely sufficient to embody in his
product the value of his labour power: if the labour power of the worker
(roughly what it cost to keep him alive and fit) was £ 3 a day and the
worker could embody £ 3 of value in the product on which he was working
in eight hours; then, if he worked ten hours, the last two hours would
yield surplus value - in this case £1.
A little further on Marx expanded on the nature of this surplus value
as follows:
During the second period of the labour-process, that in which his
labour is no longer necessary labour, the workman, it is true, labours,
expends labour-power; but his labour being no longer necessary labour,
he creates no value for himself. He creates surplus-value which, for the
capitalist, has all the charms of a creation out of nothing. This portion
of the working-day, I name surplus labour-time, and to the labour
expended during that time, I give the name of surplus-labour. It is
every bit as important, for a correct understanding of surplus-value, to
conceive it as a mere congelation of surplus labour-time, as nothing
but materialised surplus-labour, as it is, for a proper comprehension of
value, to conceive it as a mere congelation of so many hours of labour,
as nothing but materialised labour. The essential difference between
the various economic forms of society, between, for instance, a society
based on slave-labour, and one based on wage-labour, lies only in the
mode in which this surplus-labour is in each case extracted from
the actual producer, the labourer.^196