PREFACE  TO THE SECOND  EDITION



                       (1879)



In preparing this second edition  certain new sections

have been  added, the most  important of which are

those treating of the dimensions of economic quantities

(pp. 61-69, 83-84, 178-179, 232-234).   The subject, of.

course,  is  one  which  lies at the basis of all clear

thought  about  economic  science.  It  cannot  be sur¬

prising that many debates end in logomachy, when it

is still  uncertain how many meanings the word value

has,  or  what kind of  a  quantity utility  itself  is.

Imagine the mental state  of astronomers if they could

not agree among themselves whether Right Ascension

was  the name  of a heavenly body, or a force or an

angular  magnitude.   Yet this  would  not  be worse

than failing to ascertain clearly whether by value we

mean a numerical ratio, or a mental state, or a mass of

commodity. John Stuart  Mill tells us explicitly1 that

" The value of a thing means the quantity of some

   1 Principles of Political  Economy, book iii.  chap. vi.  sec. i. 1.

This definition occurs at the beginning of a carefully prepared summary

of the principles of the theory of value.