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ratio ; and in the next place, by the introduction of a third 
party entitled to a fixed toll as rent or interest in terms of 
the standard. In this case it is clear that, were the standard 
to continue to elongate, the landlord or mortgagee would 
ultimately reduce the producers to a condition of serfdom, 
by absorbing all the product of their labour. 
Proceeding now from the concrete idea of length to the 
more abstract and complex notion of value, we find the 
problem further complicated by the fact that we have to 
abandon the notion of the standard as a thing apart. To be a 
measure of value in exchange, it is in the nature of the case 
that the standard must itself be an exchangeable com- 
modity; in other words it must have currency. Moreover, 
as, under the conditions of advanced civilisation, direct 
barter is impossible, it must have the attribute of legal 
tender. Finally, as the last-named condition implies that 
exchanges cannot be simultaneous, and, moreover, the con- 
ditions of continued production imply prudential provision 
for the future, involving rent and interest, or, to sum up 
the whole in a single phrase, the arrangement of fixed 
payments, if not in perpetuity, at least for considerable 
periods ahead, it follows that the standard ought, if it is to 
be a perfect and just measure, to have the quality of relative 
quantitative invariability. 
The previous metals — gold and silver — have currency not 
merely by what is called the common consent of mankind, 
but because of their intrinsic utility as metals. This latter 
quality is a guarantee of their currency ; their acceptability 
in exchange does not depend merely upon fashion. Like 
corn as food, so gold and silver as malleable metals are 
assured of a permanent utility, and as labour is required for 
their production, they are also assured of a permanent value 
