THE “QUANTITY THEORY” 63 
other is more impressed by the importance of B, 
and therefore says ““ X depends upon B, other things 
(including A) being equal.” The first writer then 
goes about recruiting adherents to the “A theory 
of X,” while the other seeks support for the “B 
theory of X,” though all the time the two theories 
are really not opposed to each other, but are only 
two parts of the same theory, each of which is taught 
by an expositor who thinks less of the other part. 
Just so the Quantity Theory of the value of money 
singles out quantity as the thing on which the value 
of money may be said to depend, other things 
(including Demand) remaining the same. It would 
be very astonishing if this were not true, since it is 
true of every commodity other than money that its 
value depends on its quantity, other things (including 
demand) remaining the same. 
Certainly in the case of other commodities we are 
in the habit of speaking of supply ”’ rather than of 
“quantity,” but the difference in wording does not 
seem to be important. The stock of some things 
(such as milk, or even wheat) on hand at any one 
moment is so small in proportion to the annual 
produce of the article, that we think of the stream of 
produce as furnishing the supply. Of other things, 
such as land, buildings and railways, the annual 
production is so small compared with the stock in 
existence at any one moment, that we think of the 
stock, rather than the annual produce, as furnishing 
the supply. In regard to this second class, we talk 
readily of the supply being increased when we mean 
that the quantity in existence has been increased. 
A country is “ well-supplied ” with" railways or a 
town with a particular kind of house when the 
quantity of these things is great. Currency is one 
of the durable instrumental goods, such as houses, of 
which in ordinary times the stock at any moment is