kinds of wealth: those which relate to the details of particular trades
or employments forming the subject of other and totally distinct
sciences.

If, however, there were no more in the distinction between Political
Economy and physical science than this, the distinction, we may venture
to affirm, would never have been made. No similar division exists in any
other department of knowledge. We do not break up zoology or mineralogy
into two parts; one treating of the properties common to all animals, or
to all minerals; another conversant with the properties peculiar to each
particular species of animals or minerals. The reason is obvious; there
is no distinction _in kind_ between the general laws of animal or of
mineral nature and the peculiar properties of particular species. There
is as close an analogy between the general laws and the particular ones,
as there is between one of the general laws and another: most commonly,
indeed, the particular laws are but the complex result of a plurality of
general laws modifying each other. A separation, therefore, between the
general laws and the particular ones, merely because the former are
general and the latter particular, would run counter both to the
strongest motives of convenience and to the natural tendencies of the
mind. If the case is different with the laws of the production of
wealth, it must be because, in this case, the general laws differ in
kind from the particular ones. But if so, the difference in kind is the
radical distinction, and we should find out what that is, and found our
definition upon it.

But, further, the recognised boundaries which separate the field of
Political Economy from that of physical science, by no means correspond
with the distinction between the truths which concern all kinds of
wealth and those which relate only to some kinds. The three laws of
motion, and the law of gravitation, are common, as far as human
observation has yet extended, to all matter; and these, therefore, as
being among the laws of the production of all wealth, should form part
of Political Economy. There are hardly any of the processes of industry
which do not partly depend upon the properties of the lever; but it
would be a strange classification which included those properties among
the truths of Political Economy. Again, the latter science has many
inquiries altogether as special, and relating as exclusively to
particular sorts of material objects, as any of the