PREFACE. 
vii 
The causes of value have been also too neg- 
ligently passed over. Little inquiry has been 
made into the nature of these causes, or their 
mode of operation, and to this slightness of 
examination may be attributed several import- 
ant errors, manifested in attempts at undue 
generalization, in perversions of language, 
and in the rejection of circumstances which 
have a real and permanent effect. 
A singular confusion has also prevailed with 
regard to the ideas of measuring and causing 
value, and in the language employed to express 
them. The perpetual shifting from one notion 
to the other, the use of common terms for both 
ideas, and the consequent ambiguity, vacilla- 
tion, and perplexity, exhibit a remarkable 
picture of the difficulty of thinking with close. 
hess, as well as of the defects of language as 
an instrument of reasoning. 
The confusion and obscurity, which mark the