100 MODERN MONETARY SYSTEMS
The classical theory fails through lack of information
as much as through carelessness in stating each problem
exactly, and in ascertaining the actual conditions and the
legal prescriptions which determine the actions of man,
who is often unconsciously the originator of economic
phenomena. But neither is it certain that the fundamental
ideas, from which its conclusions are deduced, are quite
firmly established; and they must themselves be subjected
 to criticism.
In the remainder of the work we shall therefore follow
a logical order ; and in the following chapter, which will be
devoted to currency and prices, we shall attempt to discover
 the fundamental ideas of the Quantity Theory.
Thereupon we shall state the theory of the exchanges
and its corollaries.
Finally, we shall attempt, with the help of the data
which have been ascertained, to define the idea of money
and that of a monetary standard.