186 MODERN MONETARY SYSTEMS 
observed that this ratio, which is generally determined with 
the help of money, is not arrived at merely by chance. It 
may be said that this scale of values, which can be deter- 
mined with the help of money as between different com- 
modities at a given moment, or these changes which with 
the help of money can be measured from one moment to 
another, are built up on some of those characteristics 
which writers on the theory of value have attempted to 
analyse. But without introducing here any discussion of 
such theories it may be said that even if these character- 
istics may be attributed both to money and to commodi- 
ties, they are in all cases relative and variable and could not 
give to the measure of exchange value a basis comparable 
with that given by length to the measure of length. And 
even admitting that the theory of value which attempts to 
reduce all value to mere utility has been successful, this 
utility is relative and varies with the ratio between the 
supply and demand. Finally, it should be observed that 
money, being a measure of values, is at the same time an 
instrument of exchange, and that according as it is issued 
in larger or smaller quantities it affords more or less pur- 
chasing media. As we have seen, the latter may be in- 
creased so as fo change the rate at which transactions take 
place and which money, as a measure of values, is intended 
to register. This is the chief reason why money appears to 
be an unstable standard. 
In fact it is not obvious a priori that it is unstable in all 
circumstances ; but it may be said that, given its general 
character, it does not imply stability and sometimes there are 
serious reasons for believing that it is itself responsible for 
changes in the exchange ratio which it measures. Hence a 
standard of value cannot be expected to provide, like units 
of length or weight, a fixed point of comparison for the 
relations which it serves to establish. We all know what is 
the length of a metre independently of the data which it 
gives as to the length of the objects it measures, and if we 
demonstrate by means of a metre that a wall in process of 
building has been raised or that a tree has grown, it will 
occur to nobody that the metre may have become shorter. 
1 We neglect here the very small changes to which the metre may be