. If
there were no other objection, the fact that the word capital is
never used exactly in the same sense in the two spheres of
phenomena must give us pause. True, all capital which serves
as a tool of production is also capable of bearing interest, but
the converse is not the case. A dwelling-house, a hired horse,
a circulating library bear interest to their respective owners
without having anything to do with the production of new
wealth. If, in the sphere of distribution, the conception of
capital thus embraces objects which are not capital in the
sphere of production, this alone is sufficient to show that the
bearing of interest cannot by itself be an indication of the
productive power of capital. We have not to deal with one
motive power transmitting itself to two different spheres; not
even with two groups of phenomena which have grown up so
intimately connected that the explanation of the one is got
fully and entirely through the explanation of the other; but
with two distinct classes of phenomena. Thus we have two
distinct subjects, which give us material for two distinct
scientific problems; and finally, we have to seek for the
solution of these problems by two distinct and separate roads.
It so happens, however, that these really distinct problems are
accidentally linked together by one name; they are problems
of Capital. It may be that, besides identity of name, we shall
find many inner relations between the two series of phenomena
and the two problems;—our investigation shall decide
that later. But such relations are yet to be discovered; they
must not be assumed; and unless we would give up all idea
of being unprejudiced in our quest and in our conclusions, we
must begin the inquiry free from any preconceived opinion of
a necessary identity, or even of an exact parallelism, between
the productive efficiency of capital and its power of bearing
interest.