ddicted to such studies do not
expect to master them without undergoing special discipline; and, having
precisely defined the terms, they acquire the habit of thinking with
them according to their assigned signification in those investigations
to which they are appropriate. It is in the Social Sciences, especially
Economics and Ethics, that the use of popular terminology is at once
unavoidable and prejudicial. For the subject-matters, industry and the
conduct of life, are every man's business; and, accordingly, have always
been discussed with a consciousness of their direct practical bearing
upon public and private interests, and therefore in the common language,
in order that everybody may as far as possible benefit by whatever light
can be thrown upon them. The general practice of Economists and
Moralists, however, shows that, in their judgment, the good derived from
writing in the common vocabulary outweighs the evil: though it is
sometimes manifest that they themselves have been misled by
extra-scientific meanings. To reduce the evil as much as possible, the
following precautions seem reasonable:

(1) To try to find and adopt the central meaning of the word (say rent
or money) in its current or traditionary applications: so as to lessen
in the greater number of cases the jar of conflicting associations. But
if the central popular meaning does not correspond with the scientific
conception to be expressed, it may be better to invent a new term.

(2) To define the term with sufficient accuracy to secure its clear and
consistent use for scientific purposes.

(3) When a popular term has to be used in a sense that departs from the
ordinary one in such a way as to incur the danger of misunderstanding,
to qualify it by some adjunct or "interpretation-clause."

The first of these rules is not always adhered to; and, in the progress
of a science, as subtler and more abstract relations are discovered
amongst the facts, the meaning of a term may have to be modified and
shifted further and further from its popular use. The term 'rent,' for
example, is used by economists, in such a sense that they have to begin
the discussion of the facts it denotes, by explaining that it does not
imply any actual payment by one man to another. Here, for most readers,
the meaning they are accustomed to, seems already to have entirely
disappeared. Difficulties may, however, be largely overcome by
qualifying the term in its various relations, as