182 
POLITICAL ECONOMY 
using machines and tilling the ground, and 
so forth, that the real income of the com 
munity is maximised. When we say that 
the marginal utility of capital is a certain 
amount—which means that interest must 
be that amount—we mean that the employ 
ment of another increment of capital (i.e., 
the employment of a little more labour in 
making machines and so forth) would raise 
the net income of the community by that 
amount. That is to say, there will be a net 
gain from employing more capital so long 
as the marginal utility of capital is above 
zero. Why, then, is not capital applied to 
production until interest drops to zero ? 
The answer cannot be given in a single 
sentence. In the first place, sacrifice must 
be made in the form of deferment of con 
sumption, or saving, some time before the 
reward is reaped, and the share of this sacrifice 
which fell to the poorer classes might be 
quite beyond their saving powers. Robinson 
Crusoe could not have made all at once 
every kind of instrumental capital that he 
needed. He had to calculate the time he 
could spare from rest, recreation and the work 
which was more immediately productive of 
what he wanted to live. In the second 
place, the providence of many people is